I've updated the sciences page of my library with some terrific finds courtesy of Google video and Cosmos studios. Carl Sagan's Cosmos series, with the exception of three episodes, is up and ready for viewing. There are ten of thirteen posted, each an hour long (plus an excerpt from one of the episodes where Sagan explains the Drake equation - posted below). Interesting that despite the series being nearly thirty years old, the episodes still contains a wealth of very usable knowledge.
A little newer, here's the Black Holes and Beyond episode from Stephen Hawking's 1997 PBS series. Fifth of six episodes, it's the only one I've found so far.