Twitter is a popular social networking utility that's gaining popularity as a micro-blogging tool. Registered users can post messages -- also called Tweets -- via the Web interface, but many prefer to use desktop applications that offer additional functionality and move Tweeting out of the browser entirely.
Qt Twitter Linux is a barebones KDE client developed with Qt and C++. Since it was built using Twitter's APIs, messages sent via this tool appear instantaneously in Twitter's timeline as if they were sent directly from the Web-based interface (all Tweets show what app the sender uses by default). While Qt Twitter Linux doesn't come with handy features such as search and archive, it's great for dashing off quick messages.
Twitux is a Twitter client designed especially for the GNOME desktop. It has several basic features, including direct messaging, notification of friend updates, timeline auto-update, and a system tray icon.