Twitterers who are not humans or individuals (generally speaking):

Applications, etc. 

• Adium
• Amazon.com Bargains
• Amber_Alert
• Billable
• Flackr
• GasCalc
• Hazel
• Internet Explorer
• iTweet
• IWantSandy
• Less Accounting
• Loved by Less
• MarsEdit
• MoniTwitter
• Mozilla Firefox
• OnBroadway
• RapidWeaver
• Ruby JobMotel
• Spaz
• StrawPoll
• Titletown
• Twadget
• tWAITter
• TweetLater
• Tweet Scan
• Twinkler
• TwitterJobSearch
• TwitterPost
• Twitterrific
• TwitterSecret
• Tw1tterverse
• twrl
• WordPress Twitter Widget
• YikesSalon
• Zotero

Bots 

• has been moved

Comedy 

• Insults (Learn from a master and get insulted 3x a day- often explicit)
• MySpace Comedy UK - www.twitter.com/myspacecomedyuk

Contests 

• Smith Mag
• ONE Condoms Design Contest

Employment

• Aquent (Company Feed)
• AT&T (Company Feed)
• Global Twitter Job Feed Directory
• Montreal Jobs (Location Feed)
• Télé-Ressources (Company Feed)
• TwitHire (Job Board)

Events 

• ApolloCamp
• BarCamp
• BarCampMilwaukee
• Bonnaroo
• C4
• ETECH
• GBTweetup
• IA Summit
• pl0gbar
• SEDS International Conference
• STIRR
• SXSW
• Under The Radar
• Gnomedex
• YearlyKos Convention
• see also: Events

Libraries

• Allegheny County Library Association (Pittsburgh)
• Casa Grande Library
• Cleveland Public Library
• Nebraska Library Commission's Ask A Librarian
• Queensland University of Technology (QUT) (Australia)
• Twewey (the Dewey Decimal Classification system in daily chronological tweets)
• UIUC's Undergraduate Library

Literary 

• Affirmatron (motivational quotes)
• KidderLit (first lines of children's books)
• ReadingUlysses (on the James Joyce novel)
• ESVDaily (verses from the English Standard Version of the Bible)
• Twaiku (see also Twaiku)
• TwitterLit (first lines of books)
• twitterfiction (original nanofiction)
• raconteur (a twitter poetry jam * in ur archives, reading ur poems)
• everyword every word in the English language

Movies and TV

• Ghost Whisperer
• IMDb (quotes, birthdays, news & more)
• The Matrix
• Twitterflix (Read the quote, guess the movie game.)
• MrMovie (movienews feed, check MrMovie.com)
• Drive (producer Greg Yaitanes twittered during the show's premiere)
• see also: Celebrities
• WooMe: reality TV on the web via live voice and video chat sessions

Museums 

• The Bakken Museum
• Brooklyn Museum
• 24 Hour Museum (UK only)

News Services

• has been moved

Organizations, Companies, Blogs and Websites

• has been moved

Transportation

Air

U.S.

• Albuquerque International Airport
• Baltimore Washington International Thurgood Marshall Airport
• Boston, Logan International Airport
• Burbank-Glendale-Pasadena (CA), Bob Hope Airport
• Chicago, Midway Airport
• Chicago, O'Hare International Airport
• Dallas-Ft. Worth Airport
• Houston George Bush Intercontinental Airport
• Houston William P. Hobby Airport
• Las Vegas, McCarran International Airport
• Long Beach (CA) International Airport
• Minneapolis-St. Paul International/Wold-Chamberlain Airport
• Newark Liberty International Airport
• New York, LaGuardia Airport
• Ontario (CA) International Airport
• Orlando (FL) International Airport
• Phoenix Sky Harbor International Airport
• Portland International Airport
• Providence (RI) T.F. Green Airport
• Raleigh Durham (NC) International Airport
• Washington Dulles International Airport
• Washington, DC, Ronald Reagan Washington National Airport

Non-U.S.

• Barcelona International Airport
• Beijing, Capital International Airport
• Buenos Aires, Ezeiza Airport
• Glascow International Airport
• Hong Kong International Airport
• Johannesburg OR Tambo International Airport
• London, Heathrow Airport
• Montreal, Pierre Elliot Trudeau Airport
• Moscow Sheremetyevo Airport
• Munich International Airport (Franze Josef Strauss International Airport)
• Paris, Roissy Charles de Gualle Airport
• Rio di Janeiro, Antônio Carlos Jobim International Airport
• Rome, Leonardo da Vinci Flumicino Airport
• Samoa Lalomalava Airport
• Shanghai Pudong International Airport
• Singapore Changi Airport
• Tokyo, Narita International Airport
• Toronto, Lester Pearson International Airport
• Vancouver International Airport
• Zurich International Airport

Railway

U.S.

• BART (San Francisco subway)
• Caltrain (SF Bay Area train)
• WMATA (Washington, DC subway)

Non-U.S.

• Kansai, Japan train
• Kanto, Japan train

Roads

U.S.

• Oregon Traffic
• Traffic from The Oregonian
• Sacramento, CA Traffic
• Tucson, AZ Traffic

Non-U.S.

• London Traffic
• Singapore Traffic
• UK Traffic

Weather 

• has been moved

Other 

• Flying Spaghetti Monster Flying Spaghetti Monster
• Don Quijote Spanish Word of the Day
• Pun of The Day New pun added daily.
• ReadyReady (inexplicable numbers)
• Red Swingline Stapler
• Yasu A Ball Jointed Doll owned by dementia