Well, when I rehearse sermons and the like, and I need to see how my form is, I just open Photobooth, click the movie option, and record. In your pictures folder, there is a folder called "Photobooth" and any movies you record in photo booth will be there. If you run Snow Leopard or Lion, you have Quicktime X, which allows you to trim out annoying things (like the beginning where you're walking away from the computer to where you want to go). It's a pretty painless process, and I'd recommend you give it a shot to see if it works with what you need to do.