Thats great stuff how did you animate it though??
Firstly I set up the film viewer to give the best zoom and perspective. Then playing back the film, I used a screen grabber that allowed me to take several screen shots per second and save them automatically. Then I edited the screen shots where I wanted text and lines as though I was working on a blackboard. Lastly I put the screen shots back together as an animated gif, but with longer delays for the shots where I added text. Then I just linked to the animated gif.
There must be a wide variety of software that can be used. I used some very dated versions of Hypersnap, PaintshopPro and AnimationShop. I notice that Tango figured it out and has been posting similar images but I suspect using different software.
Hope that helps...
Badboy