I like listening to historical podcasts, and my favorites are "The History of Rome" (which has finished) and its followup "The History of Byzantium" and "Hardcore History" . I've heard good things about "Revolutions" by the creator of "The History of Rome" but I haven't checked it out yet.
Also I've been enjoying "Fall of Civilizations" a lot, but so far have only listened to a few of the episodes.