Any phone Android Blackberry iPhone and iPod touch  Symbian + Windows Mobile + Flash Lite Windows Mobile Symbian Unsorted

Any phone

• Mobiscape - A feature-rich Twitter client for J2ME / Windows Mobile / BlackBerry phones (over 300+ phones supported!)
• BuzzerTwit.com - Submit your Twitter Mobile Apps (All in one App repository for Twitter widgets, plugins, extensions, etc)
• QuaseFree - é a primeira aplicação brasileira que permite a atualização do twitter pelo celular. Além disso possibilita o envio de mensagens diretas entre usuários do twitter.
• ArrivedOK C2S - an experimental Twitter messaging application that lets you tweet from your cell phone for free even from abroad, avoiding charges for SMS, voice or data transfer. Based on Call-2-Service and USSD mobile technologies. 
• dabr - The best Mobile Web App for Twitter to date. Described as 'm.twitter on steroids', dabr is ad-free and provisioned for S60, Android, the iPhone and Blackberry... 
• FeedTwit can send your @ replies or mentions to your phone as a text message or SMS.
• tuitwit - Tuitwit is  Twitter Mobile Web App for low/mid end phone users. It features retweet, reply to all, trace, automaticly detect your friends location, update your location manually without GPS, show @twitpic, @tweetphoto, and @yfrog thumbnail pictures, and a fast feature to switch your logged account. Their focussed for volume based connection users for saving their browsing cost.
• trottr - „Hear I am!“ - trottr allows you to send audio messages to anybody around the world. Any time - and from anywhere. All by making a simple phone call. Whenever you feel like it, you can let your friends, family and colleagues listen in on your life – true to our motto. All your updates are being sent to your twitter timeline automatically - you can even answer by phone.
• Tweete - Mobile Tweete is a lightweight mobile website. It features user timelines, replies, direct messages, users, favorites. It focuses on being a super-lightweight client.
• Twitizer - An exciting new service that enables you to send long texts, photos (or other pictures; optionally geotagged), video clips and/or audio clips (or podcasts) from your mobile phone or PC and get them published on Twitter, without any special application. All you need is e-mail, MMS or a browser.
• twitwoop - Call a twitwoop number and leave a voice message to your followers. twitwoop let's you send voice messages to your Twitter timeline. Register your phone and link your number to your Twitter account. After that you can call by phone, speak a 140 second message ;-) and wooops, it's in your Twitter timeline. Some ideas: let your friends listen, when you are at the U2 concert, let them hear some ocean breeze, sing a song or tell a joke. It's up to you.   
• TwitterNeni - A service that provides an SMS gateway for mobile phones in Guam and the CNMI (Commonwealth of the Northern Marianas) to be able to post status updates via SMS since Twitter's SMS service is not supported in Guam and the CNMI.  Support for receiving updates via SMS should be coming soon.
• vMagine - vMagine is a service that allows you to record videos from your mobile directly to the web. With a simple video call, you turn your mobile into an "online camera"and share the moment with family & friends

Android

• DroidIn - LinkedIn client that allows automatic posting of status updates to Twitter. Uses OAuth so you don't have to give away your password
• tDash for Android - To upload pictures to Twitter from phone. You can share pictures from your favourite camera or gallery application.
• twidroid - the #1 full-featured client for android mobile phones
• TwitteRx - the first global ready Android Twitter app for the novice to extreme user
• Twti2go -  A fast and clean Twitter client for Android powered devices. It has search, photos, URL shortener, etc.

Blackberry

• Twitterlerts - Twitter with Search and Alerts The Twitter client that tweets, searches and alerts when it finds things that matter to you 
• TweetCaster - TweetCaster is a stylish, feature-rich Twitter app for BlackBerry. Great for managing multiple Twitter accounts.
• TwitterBerry - TwitterBerry is mobile client for posting updates to Twitter. It works over the data network, so you don't need to use SMS.
• SocialScope - In private beta currently, signup for an invite on their site.
• TinyTwitter - Love twitter and love tweeting from your mobile device? But don't want to get dinged for updates and double dinged for friend updates continually arriving via SMS?
• Twibble - twibble mobile for Java enabled devices (Nokia, Blackberry, and others). It supports all important twitter functions, uploading of photos, GPS, and more.
• Blackbird - A simple lightweight twitter client for Blackberry smartphones.
• bbtweet - In short kind of works like Twitter does for SMS but with out having to pay your carrier for sms.
• UberTwitter - Location enabled twitter client with loads of features.
• YATCA - Yatca is an innovative Twitter client application for BlackBerry (OS 4.6+) that delivers updates and replies directly to your device’s inbox.
• TweetGenius - $5 on sale. A revolutionary UI with fantastic user-orientated features like the ability to compose a new tweet, start a new search, and view tracked items from any screen in the application. Shortcuts? Please. Basically every key on the keyboard is a shortcut! What about sending pictures and GPS location? Done and done.
• Tweeteev - a disruptive Blackberry and Android client for Twitter. The interface, features and experience that Tweeteev provides will totally change the way you use Twitter on your mobile phone.

iPhone and iPod touch 

• Tweets  - your "uncommon" Twitter client exclusively for the Apple iPad.  Tweets is everything Twitter in one place, with advanced unique features such as #GeoAnywhere, #StreamingTweets, #Emoji!   
• SneakyTweet  - Everything you'd expect in a top-notch Twitter app - Multiple Views, Multiple Accounts, Photo tweets, Video tweets, Integrated Web Browser, Geo-Location, URL Shortening, Translations, Editable Retweets, and more…  Plus #GeoAnywhere, #StreamingTweets, #TweetSecrets, #Emoji!  Version 2.0 just released!
• TvvitterBug - The "2010 Next Generation" Twitter Client for the iPhone, iPod, and iPad that provides a simple yet powerful interface to all of the most sought after features you want in a Twitter client - including lightning fast performance, multiple customizable views, multiple accounts, automatic language detection, translations, integrated WebView, editable Retweets,  plus #GeoAnywhere, #StreamingTweets, and #Emoji!  Version 2.0 just released!
• Tweetings - A clean, simple, easy to use and fast Twitter Client for the Apple iPhone and iPod Touch, includes push notifications, augmented reality nearby viewer, lists, retweet and everything you would want from a Twitter Client. 
• flixup! - the best source for what movies people are talking about on Twitter (ie Rotten Tomatoes for Twitter Movie Talk) 
• TweetNGo - a fast and easy to use Twitter client for the iPhone and iPod Touch designed for casual users.
• TweetTime - a twitter client with an amazing design. Supporting multiple account, uploading pictures from camera and library, uploading a map as a picture where you are, landscape keyboard... so many features. TweetTime is the sexiest twitter app.   
• TweetChat - an iPhone optimized site for tracking hashtags in real-time.
• instatweet - a push-button iphone client to instantly post messages, photo & locations.
• TweetTalk - Your Music (fade out) Your Tweets Spoken to You (fade in) Your Music. Unique way of experiencing twitter. Tweets spoken at a set interval. Plus TweetTalk has no look gesture controls for the music, great when driving or sitting in the dock (swipe up for play, down for pause, swipe side to skip, etc).
• qStatus - qStatus is the fastest, coolest and most efficient way to tweet and update your Facebook status on your iPhone and iPod touch.
• Ohpan - a personalized news browser that gets content from twitter and lets users easily tweet stories they find
• Duo - Duo is the fast and easy way to update your Twitter account and Facebook status from the iPhone.
• Mood of the Nation - Add your Mood to your Twitter updates and Facebook status messages!  See trend graphs on how others are feeling.  Receive stimulating surveys and questions.  Follow our Twitter stream at #motn! 
• politicoTracker Twitter Edition - read any US politician's tweets - plus state-wide feed aggregation
• instatweet - a push-button iphone client to instantly post messages, photo & locations.
• ooTunes Radio - An iPhone / iPod touch app audio player app that can tweet what song or radio station you're listening to.
• TwitterView - A simple iPhone App that gives the best viewing experience for your twitter updates. Full Landscape support for viewing, posting, direct messageing, and inline web browsing. Excellent for sitting down and Flicking between your tweets with a swipe of your fingers.
• Simple Tweet - a simple iPhone application from rhinoapps.com. It allows you to explore, post, remove friends and add friends from your iPhone.
• Tweet & Speak - an iPhone app that gives your twitter feed a voice using text-to-speech technology. Hear what everyone is tweeting. Great for hands-free!
• TweetDeck - shows you everything you want to see at once, so you can stay organised and up to date no matter where you are.

  Create groups, search Twitter, manage multiple accounts and easily post your tweets or share photos, link and much more. Plus sync your existing TweetDeck columns between your desktop and iPhone. Nice and easy.

• TweetPocket - TweetPocket is a fast, fun, easy to use Twitter app for iPhone and iPod touch. TweetPocket shows you everything you could possibly want and isn't bloated with features that you don't.

• Twit Tuner - a small and free utility app for the iPhone to browse the current top ten twitter trends.
• Twittelator Pro - A best of breed twitter client for the iPhone and iPod touch, Twittelator Pro features myriad features sure to satisfy even the most seasoned of tweeters.
• Statuso - An iPhone application which allows you to update toggle on/off posting your status updates to twitter, facebook, friendfeed & yammer
• Twootball iPhone - iPhone application that tracks the scores of the NFL games and the twitter messages about those games. It also functions as client to send out tweets.
• Quotable - iPhone app that displays quotes powered by Twitter. Quotes from tweets are display in slideshow. Save quotes into local playlists, retweet quotes or share the quotes to your Tumblr blog.
• Titema - iPhone Twitter client that helps you discover new friends and unclutters your streams. It automatically selects the most interesting tweets from your friends and displays relevant messages from people you do not follow. It also features push notifications for direct messages and mentions.
• TvvitterBug - The "2010 Next Generation" Twitter Client for the iPhone, iPod, and iPad that provides a simple yet powerful interface to all of the most sought after features you want in a Twitter client - including lightning fast performance, multiple customizable views, multiple accounts, automatic language detection, translations, integrated WebView, editable Retweets,  plus #GeoAnywhere, #StreamingTweets, and #Emoji!  Version 2.0 just released!
• Mail song info  You can post tweet, mail and SMS song in your iPod library. You can choice songs using both now-playing method and manual selection from album list.

Symbian + Windows Mobile + Flash Lite

• MobiTile - FREE mobile application supports Twitter, FaceBook, LiveJournal and Wozai on Symbian, Windows Mobile and other Adobe Flash Lite enabled devices with key and touchscreen navigation to read and cross-post messages. [Adobe Flash Lite player 2.0 or greater requires] 
• Skyfire - Only mobile browser that supports flash for Windows Mobile and Symbian devices, features Twitter and Facebook on its hompage for easy access and quick updates.

Windows Mobile

• moTweets Experience Twitter from your Windows Mobile device! With all of the features you would expect from a great twitter application. Upload photos from your device camera and post your location.
• Twikini is a fast, small and frequently updated Twitter app written in native code for Windows Mobile
• Quakk is a very small, fully-featured and very attractive Windows Mobile Twitter application.
• TwitToday is a free Windows Mobile 5+ Pocket PC/Professional Twitter widget for posting Twitter updates from the Today screen
• Twobile is a free Windows Mobile 5+ Pocket PC/Professional Twitter client that allows users to use nearly all the features of the desktop web-based version of Twitter!
• ceTwit is a free windows mobile 6 native twitter client for windows mobile phones and smart phones
• SQIJ -- Sqij is a Windows Mobile application that supports mobile web applets. The Twitter applet makes using Twitter easy, and you can even get alerts of timeline changes and direct messages.
• Twaddle - Twaddle is a free Windows Mobile Twitter application with a smooth interface and great notifications.
• Skyfire - Free mobile browser that supports flash and features Twitter on its homepage allowing quick updates and message notfications.
• Kinoma Play - Update your status, tweet about music, videos and podcasts you love, and photo-blog your day with built-in TwitPic integration. Use built-in social search to see what the world’s saying about breaking news...or you!
• MiniTweet - Free and open source Mobile Twitter application with an Iphone like interface. Features: updates, reading, retweeting, replying, direct messages,...

Symbian

• FlyingBird's mobile - a collection of personal productivuty applications for Symbian smartphones, e.g. Money Manager, Car Expense Manager
• Gravity - a really nice client for S60v3 and S60v5. Includes support for multiple accounts, wifi, updates, searching, (un)following and much more. $10.
• Twittix is another Symbian S60v3 and S60v5 client with search, auto-update, and support for portrait and landscape mode, and the use of the accelerometer.
• Skyfire - Free mobile browser featuring Twitter on its homepage for quick updates and message notifications

Unsorted

• Twitter Mobile - mobile J2ME Twitter client featuring ReTweet, Direct Messages, @Reply, open URL, Twitpic support, following and followers, Delete confirmation and more.
• Book Price Check - a simple way to check book prices via reply and direct message to your mobile device.
• twe2.com - is a Free mobile service that allows you to receive your Twitter Alerts via SMS worldwide to any mobile device.
• TwitterMobile - A simple to use mobile application that gives the user a portal or gateway into the Twitter world of blogging and instant messaging.
• Snaptu is a free mobile service that offers you a selection of fun and userful mobile applications, including Twitter, Facebook, Sports and much more. Works on most Java phones.
• GPS Twit is an application for the iPhone and Windows Mobile that you can run on your phone to make it easy for your friends to find you. GPS Twit answers the question, "Where are you and what are you doing?"
• Geo Twit - share location info via Twitter
• Tiny Twitter is a free and full featured Twitter mobile client that runs on Windows Mobile Pocket PC and Smartphone devices (a native Windows Mobile client) and Java enabled devices (a J2ME client). 
• Locify with Twitter service - free. Locify adds gps location to your Twitter update from your phone and more - see public, user and friend timelines, profiles, ... Location Matters! Locify your Twitter.
• twitter on Mobio widget FREE DOWNLOAD GetMobio lifestyle portal has several mobile widgets including twitter on Mobio! Supports 100+ mobile phones [Java + BlackBerry + Windows Mobile phones]. twitter on Mobio widget allows you to update your twitter timeline, view the public timeline, and get updates on your friends timeline all from within a fast and easy to use widget interface. You've got to check this out!
• twitter on Mobio + Cricket widget FREE DOWNLOAD The definitive portal for the global Indian has several mobile widgets including twitter on Mobio plus Cricket (IPL, test, ODI), Economic Times, Times of India and more! Supports 100+ mobile phones [Java + BlackBerry + Windows Mobile phones]. twitter on Mobio.in widget is the same as the one in the US GetMobio portal (see above).
• Cricket action on twitter Check out the cod at follow all the indian team's cricket scores from your mobile with plusmo cricket feeds
• psychzzz - An easy 1 STEP Twitter Updater for your mobile phone. Supports most major mobile phone browser. XHTML-MP verified and able to support Japanese and Chinese characters as well.
• Abiro Jitter supports most features available via the Twitter API with easy access to all features, and works on most mobile phones on the market that at all support Java. It uses your data connection instead of SMS for a lower cost and more functionality, and communicates directly with Twitter for better performance and reliability.
• Twitteresce allows Java-Enabled phones (there is a list on the web site) to receive and post tweets. Much more convienent than SMS alerts!
• Twitter2Go provides a WAP or xHTML-MP interface that works on Palm, Pocket PC, BlackBerry, and almost any other mobile phone or PDA device. No software to install!
• Twitter deBolsillo tested on a Windows Mobile PocketPC. No software to install! In Spanish.
• Twapper from 30 Boxes is a WAP browser for Twitter with image support, so you can keep up with Twitter on your mobile without the constant barrage of SMS interruptions. The 30 Boxes blog provides details of Twapper v1.0 and Twapper v2.0b. v2.0b now lets you post Twitter updates.
• Twittai is designed for Java phones, which supports most of the twitter functions like Reading Tweets (no 20 tweets limit), Update, Reply, View Archive, View Replies, View Direct Messages, View Friends' Updates and Profiles, Adding Favorites, Delete Tweets, and etc. And Twittai is now compatible with more than 200 mainstream phones and Windows mobile phones.
• jibjib is a small and fast open source twitter client for any Java-enabled phones which requires only CLDC 1.0/MIDP 1.0 and CLDC 1.1/MIDP 2.0 in recent versions.
• Twitter Answers enables you to Tweet answers and get responses. Like Yahoo Answers for Twitter, powered by Mosio.
• m.slandr.net is an enhanced mobile site for Twitter, with: replies, direct messaging, users overview, search and geo.
• twnkl.org is, like DABR and slandr, a mobile-enhanced front-end to Twitter.  Features replies, messaging, conversation view, searching (with saved searches), blacklisting (remove people you don't want to see from search results etc) and other new features.  Inspired by DABR, written from scratch in Python.  Under active development!
• moblf is a platform that enable access to FriendFeed via Twitter. Users can perform the following: Post direct messages on FriendFeed, Get updates from people they are following on FriendFeed, Get updates for a particular user they are interested in.
• Twitterpation is an iPhone application that lets you record mixed voice-and-text Tweets.
• Hahlo is a mobile application for using Twitter, great for the iPhone too.
• HelloTxt is a mobile version of HelloTxt Status Manager.
• uTweetMe is a J2ME mobile application for posting Twitter updates.
• iTwtr is an open source Twitter client for iPhones. The main thing that sets iTwtr apart from other iPhone Twitter clients is its capacity to download content in the background and save it for future viewing.
• TwitterGPS, a location-aware Twitter client which runs on smartphones which support Global Positioning Satellite (GPS). Users can exchange messages containing location links and then view these as maps - either on the phone or using a PC browser.
• PockeTwit A twitter client for Windows Mobile devices. Features a unique UI, GPS integration, Capture photos and send to twitpic, and lots more.
• TwitterText (powered by SmartTouch) TwitterText allows Windows Mobile 6 users a web-like rich interactive Twitter experience through SMS. SmartTouch is a mobile widget-platform that provides an exceptional SMS 2.0 experience for users to enjoy seamless access to branded content and services such as Facebook and Google w/out the need for a data plan!
• Twibble mobile is a twitter client for Java enabled devices. It supports all important twitter functions, uploading of photos via twitpic, GPS, and much more!
• Twitter Reader is a Web Runtime widget for smartphones built on the S60/Symbian platform (like these from Nokia). Read basic tweet feed, post tweets and @replies. Can also set a custom prefix for your tweets.
• Synble is an mobile/web hybrid application for Nokia Symbian/S60 devices. Among other things, Synble can send your @replies and DM's as a text messages to your phone for free. More info...
• Map My Tracks shares your outdoor activities in real-time and updates your location on Twitter.
• SimplyTweet - An iPhone Twitter client that supports push notifications, themes and conversation threading.
• Touch Poet an Iphone/iPod Touch app which let's you make poetry and publish it to Twitter
• twitstar is a Twitter app currently under development for Windows Mobile 6 devices, and could do with some testers!
• Coffee Buzz is the Coffee Social on your iPhone - Displays nearby Coffee Locations + All the nearby and everywhere coffee talk from Twitter. Features @replies, Twitter location updates (e.g. 'Starbucks, Boulder County.' not just "iPhone: 51.2342423, 112.01230123"). Automatically composes a 'Having Coffee' tweet using your location and favorite drink.
• YiqYaq iPhone is a mobile version of YiqYaq community radio, allowing twitter channels to be listened-to via text-to-speech audio blended with news, music, and other social audio streams.
• Gravity is a Symbian S60v3 and S60v5 (touch-screen) client with support for multiple accounts, Identi.ca, TwitPic, and intuitive search features that recognize @replies and #tags in posts, as well as tweet queueing in the event of disconnection from the network.
• Zen Jar is an iPhone app that facilitates anonymous conversation between iPhone users by way of deep, interesting or otherwise meaningful thoughts.  Thoughts posted to Zen Jar are cross posted to Twitter. 
• Tweetero an open source client for iPhone/iPod Touch. Supports location, pictures upload, delayed posing (queue).
• beamME, beamME Pro lets you securely send your contact information from your iPhone or iPod touch to Twitter.
• beamME Pitch send documents directly from your iPhone or iPod Touch to Twitter.
• beamME CV sends your CV and cover letter from your iPhone or iPod Touch to Twitter.