Napkin(http://code.google.com/p/napkin-wave-gadget/) by Marcin Szczepanski of webqem, is cool gadget that was written in Adobe Flex. It allows you to do quick sketches and collaborative doodling. It provides a canvas on which we can write some sketch designed for small teams or some other people that who just want to play with it. It is good for short descriptive planning or a fun game.
I have just tried it and try to make it useful, i try to create a simple usecase to try its usability, Look at what ive got:
Simple Student Registration Usecase
It was pretty simple and easy to use. Everyone can edit the canvass at the same time. One downside of this gadget is the lack of an erase function. It would be better if the author can add it on his next release.