There's nothing like a fast upbeat tune to accompany any workout, but sometimes what keeps you going is a good book. I've recently been trying out audiobooks for my treadmill runs, and so far I'm a fan of "reading" while running.
Associating my runs with a book means that I'm always eager to keep going, so I'll find out how a suspenseful chapter will end or because I'm in the middle of listening to a humorous story. It also helps me look forward to a workout even when I'm telling myself there are many other things I'd rather be doing.
I still like to exercise to music (not to mention reality TV), but lately listening to David Sedaris essays on my iPod has been my motivator (and not only that, has kept me in a good mood while roaming the gym!). What do you like to listen to while you work out?