I just started a trial membership to Audible the other day, and downloaded a couple of books for $1. I went for a walk this evening and listened to one of them, and I think I'm going to put the other one on my player and listen while riding. Music is good for motivation and all, but the book was an easy way to take my mind away from everything, and once I'm on the bike path (out of traffic) I think that can be invaluable on a nice long ride. If my mind can stop concentrating on what my body's doing, the body seems to do fine on it's own.