My wife and I are members of Audible an online site for books "on tape" which you are able to download to an IPod, etc. Have recently been getting a lot of Heinlein books, and am loving listening to them as I jog at the gym, or drive to a jobsite. The stories, even though many were written before spaceflight was in full swing are great studies in human nature. I even found a series of his short stories which was acted out like an old time radio show. Definately good listening!