Alltray has been added to Debian unstable main.
With AllTray you can dock any application with no native tray icon (like Evolution, Thunderbird, Terminals) into the system tray. A high-light feature is that a click on the “close” button will minimize back to system tray. It works well with Gnome, KDE, XFCE 4*, Fluxbox* and WindowMaker*
Tried it and will continue to use it, I have an uncrowded window list in my panel now, specially the
“close button will minimize back to system tray” feature rocks. 🙂