Discover the Universe at Academic Earth

This new website was just launched and gives you quick access to many video lectures from America's best universities. Subjects include astronomy, biology, chemistry, computer science, engineering, mathematics, physics, philosophy, and much more! Link:

http://www.academicearth.org/

I have sampled a few of the computer science lectures (my field) from Harvard and found them informative and entertaining. Example: Introduction to Computer Science (David J. Malan)