*** THIS PROJECT IS DEAD ***
But try http://drawpile.net/ instead! It's also open source and has made a 1.0 release.
CjopazeDraw is a real-time Internet collaborative drawing tool in the vein of openCanvas, pchat, or flockdraw, but designed with full cross-platform thick-client graphics tablet support, fast synchronising, and per-user undo and redo.
- Real-time network-collaborative drawing