Sketch Pad is an open-source Desktop Gadget for Google Desktop that I knocked up one weekend in the summer of 2006 for the Google Desktop Gadget Contest. It's written in Javascript and is really a proof more anything that Javascript is sufficiant for most gadgets.
Sketchpad allows users to sketch their thoughts down on a small canvas and are able to collaborate with other users on a shared canvas via Google Talk. Since it's release at the end of August 2006 the gadget has attracted over 22,000 downloads as of September 2007.