Users who have installed QuickTime 7 Pro the $35 upgrade to QuickTime that adds authoring capabilities will gain the ability to create video and audio files that can be played back on compatible iPods.
A tutorial on creating video for iPods has been put up on the Apple Web site. It's called 'Creating Video Podcasts for Mac OS X', though it's just as relevant for creating iPod-ready video for any delivery mechanism from transferring your own home videos to traditional download.
An important caveat, if you have not yet updated to QuickTime 7 the update disables QuickTime Pro functionality in versions prior to QuickTime 7. You need to purchase a new QuickTime 7 Pro key in order to restore that capability.
For more information see the Apple Web site.