All you need on the mac is mac the ripper (decss for the mac) which is free and dragon burn--9.95 for a competitive upgrade.
The only other thing you might need is a compression program if the movie is more than the one-sided dvd capacity (single side capacity is 4.7GB, some movies come on DVDs that are double sided and can be up to 9.5GB -- but most consumer DVD drives won't burn double sided DVDs), but mac the ripper lets you extract only the movie and not the extras if you want.
Works good to back up the kids dvd's that they inevitably ruin.
Mac the Ripper removes Macrovision protection, so you can copy from DVD to tape. It will be good to have a way to backup the kid's DVDs, or to play on the VCR (rather than buy another DVD). All legal so long as its our use.
Update 1/2/06: the original site has been shut down, but one can download 2.6.6 via VersionTracker.