Draw with others.
CoSketch - A multi-user online whiteboard designed to give you the ability to quickly visualize and share your ideas as images.
Draw It Live - A free application that allows you to work together with other people to draw in real time. Simply create a whiteboard and share its URL with others. No passwords or special plugs required!
FlockDraw - A web-based painting/drawing tool that makes it easy to draw with multiple people.
Scriblink - A free digital whiteboard that users can share online in real-time.