The GNOME Deskbar Applet is a really handy command center. I have just one item in my panel that does everything from calculating expressions to searching the web to running commands.
I found a neat extension that searches for uninstalled packages in the apt cache, and gives an option to install them. Unfortunately, the way that it's written makes it hang deskbar-applet for me. To fix this, I've re-written so that the installation occurs in a separate thread. Here's the fix:
Threaded Deskbar Apt Installer