I recently became a huge fan of the National Public Radio show Radio Lab, a popular-science program that makes really quite heady scientific concepts (say, the theory of relativity) understandable without dumbing them down.
If it's not on in your area, you can either stream it or download episodes from Radio Lab here. Scroll down that page a little and you'll see links to the three seasons that have aired so far. Season four begins next month.
Listen to one episode, and you'll be hooked. Season two's "Detective Stories" had me ignoring urgent business (well, eating dinner) to find out the end of the tale that begins with two people motoring down a highway in California when they spy a goat standing on the back of a cow at the side of the road. Yes, you read that correctly--and after that, it gets weird.