Speaking as a geek with a healthy respect for the law, as far as I'm concerned, if I've already purchased the movie, there's no reason why I should not be able to rip it to be able to watch it on my own iPod. I'm not gaining any sort of profit off of someone else's work. I'm not selling bootleg DVDs of the movie, nor am I downloading the films illegally; I'm simply enabling myself to be able to enjoy a film for which I've already paid (sometimes in multiple formats...I've got several movies in VHS, DVD, and now digital files) in a different format when carting along a DVD player is either impractical or impossible.
That said, you need 2 pieces of software: one to decrypt the DVD, and one to convert it to .mp4 format so it is watchable on your iPod. I use DVD Decrypter and Handbrake, both of which are extremely easy to use and are available as free downloads. There are some types of software that will both decrypt and encode, but I've never had any success with any of them so I prefer to do it in 2 steps.
There's an extensive tutorial
here, courtesy of ilounge.com. It discusses several different types of software that others commonly use to rip videos to their iPods; DVD Decrypter and Handbrake are the 2 that I've found easiest and most efficient to use with the least number of errors (audio out of synch, etc.)
If you're pressed for time or worried about copyright restrictions, you can always re-purchase them from iTunes. Occasionally, movies will be specially encrypted or just will end up being a PITA to convert; when that happens, I just suck it up and pay for the movie again.

Sometimes it's worth the $9.99 not to have to deal with the hassle.
And hey, you can always ask for lots of iTunes gift cards for Christmas!