ZenTwitter is an amazing small script which is able to update twitter accounts without the need of having a browser window open all the time. It uses zenity and curl. (note: if you want to just use your terminal for tweeting see this posting)
Installation
Just dump it into your ~/bin directory, open it in the editor of your choice to change the username/password, make it executable (chmod a+x) and add a launcher icon to the panel/menu/desktop of your preferred window manager.
Download: ZenTwitter.tgz
Screenshots
