During my stay in Greece, I've been listening to a series of lectures I got from The Teaching Company. This site offers lectures by well-know university professors in all sorts of different fields. I chose a set in Greek history and another in western political philosophy. I downloaded them from the company website and uploaded them in my iPod, where they show up in the Audiobooks format, which means I can resume a particular lecture where I left off, even if I play some music in the interim.