The Yahoo! Search blog explains how to subscribe to keyword searches for video content with Yahoo in iTunes.
Using a a similar technique previously described here on Lifehacker in the Subscribe to free, del.icio.us video in iTunes post, you can create a feed URL of Yahoo! video content based on a search and subscribe to it in iTunes 6, automatically downloading free movies every day to your media collection. Cool.
Video Search To Go! [Yahoo! Search Blog]