For all of the bad rap that Sal Khan gets for his videos at Khan Academy, I find his endless screen trick really helpful. The ability to scroll indefinitely and record what you write on the screen can be used to demonstrate solving multi-step problems, especially helpful for math and science.
Sal uses a PC and his work is explained many places on the web. But I use a Mac and played around with the Paintbrush app. It's worked marvelously so far. I recorded the one-take no frills video above to demonstrate how to create Khan-like videos.
