The mention of Mike Seeger reminded me that he has a great video on Homespun. It's called "Old Time Banjo Styles Taught by Mike Seeger". Even if one is not planning on actually learning to play the banjo, but is interested in a variety of banjo styles, this video fits the "completely entertaining, informative and educational" category.

It features Doc Watson, Kirk Sutphin, Greg Hooven, Joe and Odell Thompson, and my favorite part of the video is Etta Baker. It is over 90 minutes long and worth every penny.