Bitshift

Podcasts are just so...2006. But serialized audio content can be quite educational as well as entertaining. For example, iTunes has a number of foreign language tutorials available. Open up the iTunes Music store, and go to Podcast -> Education -> Language Courses. There, you'll find podcasts teaching ESL, Japanese, Russian, Italian, Frensh, and many others.

Sure, you could buy a book or some training software to learn these languages, but they won't immerse you in them the way audio content will. Plus, they're free! Bonus!