One of THE MOST requested features for BigBlueButton has been the addition of an integrated whiteboard.
We've been working on this for a while now, and ... wait for it... Denis checked in the first iteration of the whiteboard code into our Google Code repository this morning.
You can try it yourself on our development build server. Whiteboard works as annotations to a presentation, so you need to upload a presentation and make yourself presenter. If you've not used BigBlueButton before as a presenter, see this overview video (3 minutes).
Here's a screen shot of the artistic work on a slide.
Whiteboard will be released as part of the current BigBlueButton 0.7 iteration.
If you try it out, give us your feedback as a reply to Denis's announcement of Whiteboard.