CBC's Ideas has a truckload of very interesting interviews. It's easily one of the best radio programs that I've heard. What's even better is that they have a huge set of past episodes available for online listening.

I recently listened to the John Ralston Saul lecture, which is quite good. I subsequently started reading his Voltaire's Bastards, which I had lying around for a long time, and which is also quite interesting. Though this review begs to differ.