There are countless ways to update Twitter these days, so I’ve tried to round up as many of the ways to update as possible. I’m sure I’ll miss a few so make sure to keep me informed by letting me know in the comments. Also, make sure follow me, LostInTech, on Twitter.
Twhirl - Twhirl is probably the most popular desktop client. It also supports TwitPic, TweetScan, FriendFeed and cross posting to Pownce and Jaiku.
Spaz - Desktop client for Mac, Windows and Linux
Tweetr - Allows you to send files to other Tweeters. It also has a built in webcam feature.
Alert Thingy - Keeps you updated on FriendFeed and Twitter. Allows you to easy upload pictures to Flickr.
TweetDeck - Better organize your Twitter friends with a great built in group feature.
Twitteroo - Displays updates without pictures (for better or worse).
Witty - Open source client for Vista and XP
bTT - Non-Adobe AIR based desktop client.
Twitterlicious - Minimalist desktop client.
Snitter - Customizable desktop client for Mac and Windows.
Feedalizr - Post to FriendFeed, Twitter, Jaiku and Flickr with this desktop client.
Posty - Has support for several microblogging services
twitbin - Creates a sidebar for Firefox to keep you updated.
TwitterBar - Post updates from your address bar.
TwitterFox - Puts an icon on your bottom bar that gives you notifications and allows you to update.
Firefox Search Plugin - Post updates from your search bar.
TwittyTunes - Show people what you are listening to.
Twitterfeed - Update Twitter with new posts from your blog.
Brightkite - Brightkite updates can be synced to update Twitter as well.
Twitio.us - Twitter + Del.icio.us
Twitthat - Bookmarklet that lets you Twit about the web pages you are viewing.
HelloTxt - Update all your services in one place
Ping.fm - Updates multiple mircoblogging services
PingTwitter - Send updates when your blog updates
Socialthing! - Lifestream plus ability to update.
Sendible - Organize your online life.