The PHDComics site has a particularly good video up on the subject of dark matter. The video is done in a style similar to the wonderful RSA Animate video series in that a fascinating talk by experts is illustrated with hand-drawn illustrations that emphasize the content of the discussion.
The video in question is a discussion between a couple of knowledgeable physicists who manage to make the subject of particle physics and astronomy comprehensible to even those of us without a PhD. The audio is a little noisy, given that it was recorded in a cafeteria, but the visuals more than make up for that.
And after you’ve watched that, be sure to check out the RSA Animate videos I mentioned above. These videos are animated versions of TED Talks, and are all worth your time….