I've taken a lot of courses from itunes U and the open courses from Stanford and MIT, and I also listen to a lot from the Teaching Company (which are not free, but are available from major libraries and tend to have better production values. I buy them.) It has greatly enhanced my life!
My dad is the person who first recommended them to me, and I have about 5 friends who have started doing this after I've loaned them a lecture series. It really helps make driving more interesting!