Hashi

With the default touchpad driver in Ubuntu, top-right is middle click and bottom-right is secondary click (right-click for most people).

This isn't mentioned in Gnome because it's supposed to be simple, but I think the package description mentioned this. I've found it quite useful because I couldn't find any way to initiate standard right-click using the keyboard (different sometimes than the 'context menu' key), and you don't need to do the complicated gsynaptics configuration stuff with touchpad memory to get it working, either. :P