I’ve heard Jamie Oliver’s name once or twice, but usually related to his cooking shows.  I don’t know that I have ever actually seen any of them.  He was recently at TED and gave an amazing presentation on Obesity and the actions that he is taking to fight it.
(*note: The video is a bit larger than the layout here, so to see it properly, you might want to click on the ted logo in the upper left or the link under the video*)

Jamie Oliver at TED on Obesity

Incredibly well done and well worth the 20 minutes.