I'm again trying to work out a conversion tactic for getting movies on to the PSP. In order to use FFmpegX to do any conversions I basically need to use a VOB. I can easily acquire VOB's from DVD's, but I can't use VOB's to make duplicate DVD's using Popcorn. FFmpegX has a lot of cool tools to convert, mux, etc. files... but ultimately I think it's just easier to use MacTheRipper twice to create a VOB and a VIDEO_TS file. It'll take less time and no more space than any of the other methods would.
