Blinkx is a site that I just heard about from Larry Ferlazzo's wonderful blog. Blinkx is a search engine for videos that does a very good job of organizing it's content. I really like how you can search by category and then watch as a wall of videos comes up playing different content at the same time.
Below is an example on a search of the term, education.
I highly recommend giving Blinkx a try by clicking here.