Search the site for tips about Handbrake. I was reading a thread here a week or two ago about iPad specific settings for it. It's great for converting video and/or ripping DVDs, and I'm sure it'll come in handy. I think the consensus was that files encoded specifically for iPad weren't compatible with iPhone/Touch video files, resulting in the need for two copies if you wanted to be able to view the movie on both devices.
I've used Toast for burning a lot and saving some disc images, but don't really know how you'd use it for converting DVDs into mp4s.