[adrianparsons]

Screenflow[1] is fantastic screencasting software. It's incredibly easy to use, and even does simple video and sound editing. I suggest recording a voiceover separately.

1. http://www.telestream.net/screen-flow/overview.htm

[jamesbritt]

Yeah, Screenflow is great. I typically record sound and video, but split them and redo the audio once the video is in shape.