Handbrake seems to be the default DVD to MPEG4 ripper, or Mac The Ripper for harder to open DVDs.
FFmpegX is a Mac OS X graphic user interface designed to easily operate more than 20 powerful Unix open-source video and audio processing tools including ffmpeg the “hyper fast video and audio encoder.
For general recording, use Soundflower to get internal sound to appear as an input in something like Audacity.