Need a program to record the screen while I narrate.

I just got a new MacBook Air. I've used Windows since Windows 3.0, and so I'm kind of lost. I am a teacher, and I had a Windows program that would essentially record the screen to .AVI including any audio input. This would allow me to narrate PowerPoint slide shows, use a pen and tablet to draw diagrams, etc. Basically, it would make a movie out of what was on the screen, including my voice over the mic.

The windows program was free. I'm wondering if there is a free (or cheap) alternative for the Mac that will do the same thing. What am I looking for? Thanks for helping out a Mac n00b!!

Profcast does this specifically, but you could probably do this with just the built-in QuickTime X player.

Screeny is good. It's on the app store at a v good price

I use iShowU, but Quicktime X's built-in screen recording feature is already on your Mac so you might want to give that a try first.