I've never used Handbrake, but I understand it's great. Another option is MPEG Streamclip (free) and the Quicktime MPEG Playback component ($20 from Apple). Here are a couple of links:

http://www.alfanet.it/squared5/mpegstreamclip.html
http://www.apple.com/quicktime/mpeg2/

I'm not sure what corner you are backed into, but if you can't extract video files from the DVDs, another software that will extract video from DVDs (which then MPEG Streamclip will turn into DV files for iMovie) is MacTheRipper. Do a search.