Earthquake - Terminal-based Twitter Client with Streaming API support. Only supports Ruby 1.9 and later.
Gwibber - Gwibber is an open source microblogging client for GNOME developed with Python and GTK.
Tui - Twitter client based on mobile.twitter.com in menu bar. Features:
TweetDeck - TweetDeck is your personal browser for staying in touch with what’s happening now.
Tweetbot - Sync your timeline across your iPhone, iPad, and Mac. Mute tweets by user, hashtag, tweet source, or keywords (including regex). 3rd Party support for image, video, read later, and timeline sync services.
Cato Social Network - Become Cato. Post Meows, get Not So Anonymous Messages, connect with other Catos & grow your online social network.