Geoffrey Grosenbach who does the popular Peepcode Screencast series, has done two 'meta' screencasts about screencasting.

In the first one done about a year ago IIRC he focused on doing it with minimal resources. He used a combination of iShowU, the tools in iLife (like iMovie), Quicktime/Quicktime Pro and a few other adjunct tools.

He just recently did a "Professional" follow up, which uses Final Cut Studio.