Seems like a jolly good idea!
Hopefully the name is self explanatory - extending the text-based world of Wiki by allowing users to draw pictures.
Experimental plugin for JspWiki at http://dannyayers.com/2003/08/jspwiki/whiteboard.htm
Anyone know of others? Yes, twiki.org has this fully implemented: http://twiki.org/cgi-bin/view/Plugins/TWikiDrawPlugin Yes, SnipSnap.org has this too http://snipsnap.org
What Should it Do?
IMO, a bit more than just freehand, but not so much that it takes time to learn...
Doesn't MoinMoin have a drawing feature?
MoinMoin uses the Twiki drawing plugin.
There are many collected notes on WikiWhiteboard at: http://wikifeatures.wiki.taoriver.net/moin.cgi/WikiWhiteboard
Have a look at http://tethys.croydon.ac.uk/democircle.nsf where we have a jave whiteboard as part of a wiki environment. Each whiteboard need a wiki title and you can use the text slot to add wiki links or create new pages.