Apple has posted a free iTunes Video page that compiles their current free video episodes available for download.
The section currently contains 14 episodes from different series. The episodes primarily include promotional videos and pilot episodes, presumably in an effort to increase the audience for upcoming shows.
Apple's video section continues to grow with regular additions to their lineup. Many still expect Apple to introduce a dedicated Video iPod in the future. Recent announcements by Seagate for 60GB and 120GB 1.8" drives have sparked speculation that Apple could use these higher-capacity drives in future iPods.