http://www.ted.com/

Of all of the video sites on the web ted.com is almost certainly the most intellectually stimulating. TED (Technology, Entertainment, Design) conferences bring together today’s greatest thinkers and achievers from a range of domains, and invites them to address the audience for 15 minutes.

The majority of talks are by leaders in their field, presenting some of the most interesting and groundbreaking developments. The videos provide great starting points for discussions, and are often highly inspirational. One of my favourite things to do of an evening is turn the TV off, and simply watch TED videos: I can almost feel my brain getting stronger.