My colleague, Leon, and I have been experimenting with LectureScribe, a software tool written by Brian C. Dean, from Clemson University. LectureScribe enables one to produce an animated "whiteboard lecture" using a tablet PC complete with voice recording. It saves the video as a Flash file (.swf) so can easily be viewed using a web browser.
LectureScribe is surprisingly easy to use, comes in a single 4.3 MB .exe file that can be easily downloaded and run without any installation ... and it is FREE.
If you don't have a tablet-PC you can use your mouse (which doesn't work real well), or an external pen-based slate. We are testing the wireless CPS Chalkboard tablet from eInstruction. It is a little pricey at $350, but works really well.
Here is an example that Brian Dean posted using LectureScribe. You won't understand a word of it. But it gives you a sense of what this software can do. To start the video you will need to click the play button at the bottom of the window.
Here is an an example that I posted showing how one uses the Pythagorean Theorem to find the length of a missing side of a right triangle.