Those of you following the posts on video abstracts/video blogging on n-Category Cafe, God Plays Dice, and The Secret Blogging Seminar (and perhaps other blogs that I didn’t see!) should look at the video Ken Baker just posted on Sketches of Topology (if you haven’t already). I think the key to this sort of thing is that when we talk math in person, we don’t look at each other – we look at the black board or the piece of paper that we’re writing on. In a math video you only need to see the piece of paper (i.e. the computer screen) and hear the person explaining it. Ken’s demo does exactly this.
It might also be nice to record conversations where someone explains a definition or proof to someone else, and again show the screen that they’re writing on (using, perhaps, one of these new fangled tablet PCs that I see more and more places) with the conversation playing over it. Such videos would be very quick to produce but could probably be very useful as supplements to books and papers. Just a thought.