Google Desktop: Google application for twitter let others know what are you doing? Read and update Twitters right on your desktop! 
Autopilot Tweet - Full Twitter automation software for Twitter marketing includes a Twitter Friend Adder / Follower Adder, auto follow, follow by keywords, follow your followers, auto unfollow, schedule your tweets and automate most of the mundance daily chores of managing your Twitter account. You can automate Twitter for an extremely affordable price.
Catfood Follower - desktop Twitter tool for following new friends that follow you and removing friends that don’t follow you back.
Friendbar- A Firefox toolbar that is the best way to follow Twitter & Facebook updates, and post to Twitter and Facebook. 
GeoTweeter - Puts the ‘where’ into your tweets! Messages automatically include a ‘schmap.me’ link, showing followers your exact location with a configurable map icon: say more about places you visit with an optional photo and star rating.
iClippy - Windows application that provides a transient online clipboard for the images, making copy-and-paste operations work online as seamlessly as it does offline. There’s a “post to Twitter” option as the image gets uploaded, makes posting visuals to Twitter a snap
JabberTwitterBridge — Java application to update Twitters, Jabber’s status (google talk gtalk) and Google calendar together (for example : In a meeting until 15h12) (Twitter to google talk, google talk to twitter, google calendar to google talk and google calendar to twitter)
mTweet - is a full mobile twitter client application running on Windows Mobile 6 or higher
QckTwit – A simple Twitter app that you can activate anytime by Shift+Alt+T and it would pop up presenting a text box to enter your update quickly. As soon as you press Ctrl+Enter, it will send update to Twitter and get out of your way. Separate box for URL. If your message exceeds Twitter’s limit then it will automatically break it down in multiple twits and color those extra chars differently. Open source, requires .Net 3.5
Sociagami – sociagami allows you to manage your multiple social network statuses from one beautiful Windows application. sociagami currently supports Myspace, Facebook, and Twitter status.
TweetDeck is your personal browser for staying in touch with what’s happening now, connecting you with your contacts across Twitter, Facebook and more.
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Twitter is micro-blogging platform and one of the hottest social media platform. You can use this by joining twitter.com
What can twitter do for you?
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