TweetDeck - TweetDeck is your personal browser for staying in touch with what’s happening now.
Choqok - Choqok - KDE Micro-Blogging Client The name comes from an ancient Persian word, means Sparrow!
Tweetdeckr - Tweetdeckr is an open source Tweetdeck replacement client.
Gwibber - Gwibber is an open source microblogging client for GNOME developed with Python and GTK.
TweetDuck - Free & open source desktop client for TweetDeck
Twitterfall - Twitterfall is an excellent choice if you want something basic, free and without much branding.