TwitTray 

TwitTray is a minimalist approach to a desktop Twitter status updater. It is tiny and very fast. The program sits silently in your system tray until you want to update your Twitter status. Double-clicking the icon will pop up a small box to allow you to type in a new status or pick from a recent status. As of version 0.5 you can also view your current profile image. Future additions will include timed status changes, friend updates, better support for special/international characters and urls, and possibly more changeable settings. The ability to change your profile image by dragging and dropping a new one onto your old one is in the works, but there are severe issues with the Twitter API that are interfering with the ability for it to work properly.