Lectures from the Stanford Linear Accelerator Center including: Whispers of the Big Bang by Sarah Church, Archimedes: Accelerator Reveals Ancient Text by Uwe Bergman, Our Lopsided Universe: The Matter with Anti-Matter by Steve Sekula and The Runaway Universe by Roger Blandford. This collection is yet another great resource.

The number of great resources has prompted me to created a directory of great science and engineering webcast libraries: Curious Cat Science and Engineering Webcast Libraries. These sites have awesome science and engineering videos. Definitely worth viewing.

Related: Google Technology Webcasts - open access science posts - Google Tech Talks - UC-Berkeley Course Videos - The Inner Life of a Cell: Animation