Open Culture is a website my husband found. He's just been given his first MP3 player, a hand-me-down from our daughter, and he's become a big fan of the world of podcasts and lectures that he can download and carry it with him to listen to whenever he wants.
There is truly an impressive collection here - everything from free audio book links to foreign language lessons. It has a list of university lectures by subject from across the nation.
Television and music.
Science and law.
I warn you; it's one of those places (much like a great library) that makes you feel there will truly never be enough time in the world to explore every avenue of interest.
My oldest (age 13) has begun browsing the site. I think it would be a great resource for older kids and adults.