Here's the stuff I've been listening to in my car lately. It's very geeky. Beware.
Rick Rashid - From the Labs at Microsoft Research - some very cool stuff.
Trent Henry - Enterprise Security Architecture kinda of "heavy" but some good stuff in there.
Peter Norvig - Inside Google - need I say more? Good stuff coming from Google Labs
David Fogel - Accelerating Problem Solving - some amazing talk about machine learning algorithms
Paul Graham on Business and Open Source very insightful
Ray Kurzweil - "When Humans Transcend Biology" a totally futuristic talk, with lots of interesting questions to think about