I second Lord's recommendation. In the gym, running, or on the road I'm listening to business, sales, or online-industry audio books. At their very worst, they keep you focused and open you up to new ideas. At their very best, they are gold for expanding your business.
I'm a cheapass and don't want to pay for audio books haha. I don't have any problem buying the actual book because I feel like then I actually have something to show for the money I spent. I'm always impressed by a home/personal library of great books. A collection of CDs just doesnt have the same effect haha