My latest fascination is "In Our Time," the BBC radio program that stars Melvyn Bragg and examines historical matters with far more depth than just about anything on American radio. In recent days I've learned about Norse mythology, the Spanish Inquisition, Henry VIII's dissolution of the monasteries -- all without having to crack any pesky books!
The closest American analog I can think of is not a public radio show, as you might think, but rather "Extension 720" from Chicago's WGN-AM. I loved that show during my years in Chicago, and I still tune in from Dairyland. Like "In Our Time," "Extension 720" delves into history, and also current events, science, literature. And unlike the BBC podcasts, the live WGN broadcasts come complete with ads for Empire Carpet.