I know I'm probably behind the game in this, but I just learned approximately the coolest thing I've learned in awhile:
QUICKTIME MAKES SCREENCASTS!
Just open up quicktime, and under the File menu, you'll see New Screen Recording. How great is that!? I haven't tried it yet, but I'm assuming it's good. Just make sure that you turn on the microphone--click the little arrow by the record button and turn on your microphone.
Here's a little video that explains it:
