The PHP-GTK Community website has pointed out a small application, a cross-platform microblogging client called Nitwit.
Features include cross-platform functionality (Linux/Windows/Mac OSX), the ability to work on many protocols (like Jabber/Twitter/Jaiku) and it includes multilanguage support.
You can find out more about this simple little application on the Nitwit site as well as down load the latest version. There's also a discussion area that's been set up to allow developers and users to throw in their comments.