Academic Earth

If you are a big fan of TED talks, then I would highly recommend you check out Academic Earth 

They currently have lectures on a wide range of topics from the following institutions: Berkeley, Harvard, MIT, National Institute of Health, Princeton, Stanford and Yale.

Academic Earth was launched on January 18, 2009 and had one million site visits in its first three months, a great indication of where learning and the sharing of knowledge is headed.

You can follow them on Twitter, join their fan page on Facebook or subscribe to their RSS feed.