The latest Google Video redesign removed yet another useful feature from the interface: restricting search results to a certain category. The feature is still available, but you need to use the genre: operator in your searches. Here are some of the most popular genres:
Examples of searches:
charlie chaplin genre:movie_feature
data mining genre:educational
You can also use the genre: operator to better describe your search when you want to subscribe to a Google Video feed or to get an email alert when new videos are uploaded.
At some point in Google Video's history, you could browse videos by genre directly from the homepage, but you can still use the genre: operator without any other keyword to see popular videos from a certain category, like TV shows.