[Radix]

Grockit, a test prep startup, does this. They're setup to give test questions to be answered in a given time frame with ongoing chat between room members and there is an optional white-board for drawing on.

The drawing section isn't built by them, it's actually built by an HN poster running, I believe, ExpatSoftware. You could probably make use of his project... Actually, I checked. They're just using Twiddla. I think Twiddla is pretty much what you want. You can free hand what you want and you have an etherpad a click away. Tying it in to KA would be left.

Kamens, is there a way to view all the unanswered questions on Khan Academy? I think it might receive a fair amount of traffic if there was.

[kamens]

Not at the moment, no. We're tackling some lower-hanging fruit, but this sort of community tool is obviously on our horizon.