I've recently started backing up my commercial DVD's to my hard drive, and I'm tending to use
HandBrake for it. So far
it produces a nice compact m4v file, but I've yet to see the fruits of my intensive labours with it. And its soooo slow!
VLC can also rip DVD's and store them as an *.avi file, but it doesn't appear to compress the file output, which means that you get a horrendously big file.
K3b can also rip DVD's, but it stores each 'chapter' in the original film as a separate *.avi, which means that you need to "stitch" them together again, before they can be of any use to you in a meaningful way.