I use Clone DVD Mobile and AnyDVD, both from slysoft.com think you can buy the keys for both for something like 30 dollars as a package. I originally bought it for my ipod, but foundd it works for the iPhone as well (just drop the movie into iTunes to send it to your phone).
Thing I like most about slysoft is that the keys are good forever (well unless the company goes under), you can use it as many times as you want, and lifetime free updates on all their software. Might want to check it out. Just make sure not to by CloneDVD Mobile alone! you WILL need some sort of DVD decryption removal to use it (AnyDVD runs in the background and does this automaticly as soon as you put a DVD into your drive).
Ive been using their software for a few years now, and have to say they've done a outstanding job on supporting their software, unlike others I've tried. I don't mean to advertise for them, but been really happy with them.