HandBrake is a GPL'd multiplatform, multithreaded DVD to MPEG4/H.264/DivX ripper/converter. It was originally available on the BeOS (and still uses the jam build system that was a favorite of many developers for that OS, but now has been ported over to Mac OS X and Linux (CLI only). A Windows port is being worked on, and there is a Lite version available as well.
Resources:
- Mac Gems: HandBrake 0.9.0 - a HOWTO and presets for common encoding tasks.