Did you ever have a great teacher that just made their subject fascinating? That's what listening to Radio Lab with Jad Abumrad and Robert Krulwich is like. With their goofy wit and accessible info, I find myself amazed by science and actually learning more things about certain subjects that I remember than when I was in school. (I only had one memorable teacher, Mr Nichols, and it probably helped us to remember what he said because we all had crushes on him).
I'm listening to their archives and can already highly recommend the programs on sleep, stress, and sperm (that's three separate episodes by the way). If you've exhausted your This American Lives and have a curiosity in the mysteries of science, this entertaining show will be a god send to you.