The guys at DigitalGrabber have been kind enough to post what they're calling the "ultimate" guide to getting video to your shiny new iPod. There are plenty of freeware apps available for video conversion, & they cover a few of the options.

"This guide is going to take over all the options you’ve got and how to convert absolutely anything and everything – DVDs, TiVo video, messy AVIs, muxed MPEGs and more to iPod compatible video – all within OS X."