I've been playing with Camtasia Free (Techsmith.com), but it is a limited time trial and the actual program, while very powerful, is also nowhere close to free. They also have Jing and Snagit, lesser programs, and one of these may be free or nearly so.
The technology (in Camtasia, at least), is pretty awesome. Record the whole screen or part of the screen, plus audio from various sources. Then you get into a powerful editor where you can 'massage' what you just recorded. Then you 'produce' the resulting project into one of several formats. The latter process can take a while, at least on my old PC. Great results when you get done, though!
One would hope that the lesser programs, while not having the bells and whistles, would be as functional as Camtasia.
John