HandBrake is a fantastic little cocoa app that'll do it all for you! Very reliable, good quality rips (straight to XviD or ffmpeg), AAC or MP3 audio too.
You don't get massive amounts of control, and it's not the most efficient software in the world, nor can you specify the thread priority but it does the job, its a doddle to use, its completely free and will rip straight from the DVD.
http://www.versiontracker.com/dyn/moreinfo/macosx/21117
The best way to do it is with two little apps. One called YadeX, which will decrypt the DVD to your harddisk, and then D-Vision 3 (basically an easy to use interface for MEncoder) which will encode the VOBs to a file of your choosing. Its straightforward, and you get a lot more control. The rips are better quality (if you're playing them from your mac, using VLC or something), but they're a little jittery on my Kiss DP-500 networked dvd/divx player. As before, both apps are free.
YadeX:
http://homepage DOT mac DOT com/jibee/macetvideo/yade_X_us.0.99b.sit
D-Vision:
http://www.versiontracker.com/dyn/moreinfo/macosx/16486
I hope you're not planning on doing anything illegal...
MrJ