Here's my top ten at TED.com. I vote TED the best site on the superhighway. The coolest free video and audio talks ever. I download them for long drives.
TED stands for Technology, Entertainment, Design and it's a conference that happens in California each year with the most amazing speakers on earth... from Michelle Obama to Al Gore to Richard Branson to Bono and loads of others you've never heard of, but who are equally as fascinating.
Another fave talk is Malcolm Gladwell on the 10,000 Hour Rule (The Story of Success)
Not a TED talk but such a really interesting idea.