TED

This is Brian Greene explaining some of the basics of string theory, the dominant theory in physics capable of explaining spacetime under extreme conditions.

I've been a fan of Dan Dennett as a leading thinker in areas of evolution as well as philosophy of mind and personality. In this clip, from the 2006 TED conference, Dennett gives a presentation soon after mega-church pastor Rick Warren has spoken. Dr. Dennett is always a treat, but this one, dealing with evolution, creationism, and the role of religion, is of his best.