+1 for The Teaching Company. I've spent many hours sitting in traffic while learning about music, linguistics, economics, philosophy, any many other topics. The

+1 for The Teaching Company. I've spent many hours sitting in traffic while learning about music, linguistics, economics, philosophy, any many other topics. These are recordings of lectures for college-level courses, purpose-made for canned consumption. Also consider regular audiobooks. I have a subscription to Audible.com (site is lame, product is good). These aren't limited to the latest thriller novel: there are plenty of good non-fiction books available.