The docking utility KDocker that let’s you dock any window to the system tray.
Yakuake which I wrote about in a previous entry and is a very nice Terminal/Console activated (by default) by F11 and hides at the top of the screen until pressing F11 and it simply scrolls down.
Kirocker which is a visually hot music displayer that when playing music (I use Amarok) and activated will function sort of as a screensaver (using the whole screen) with information about the song that is playing at the moment.
Thunderbird (also written of earlier) let’s you connect to your e-mail accounts such as Gmail, Hotmail/Live, Outlook and more.