I buy a lot of DVDs from Japan, but unfortunately they are often region 2 restricted. In order to play them back on an American DVD player, I need to "rip" them and then burn them back as unrestricted (region 0) DVD-R.
The program I use on the Mac is MacTheRipper. Unfortunately, the program development on it seems to have stalled, and it isn't keeping pace with the latest encryption and anti-hacking technologies being used by some companies.
In these cases, I switch to my Windows XP operating system (under VMWare Fusion) and use a program callled DVDFab. It's commercial (i.e., costs money) but there isn't a DVD out there that it hasn't cracked. It works great under Fusion -- and it even writes the VIDEO_TS files out to a shared folder on my Mac OSX partition, so I can then write them out immediately using Toast, or use Handbrake to further compress them.
(You can compress to H.264 inside of DVD Fab but I think that Handbrake's algorithms are better and you have more control over the process).