Uhm... the pirate bay...
Either that or if you want to take the time, you can often get audio books from the library and copy'm or rip'm.
To date, I have listened to college lectures people had published on the pirate bay, a horrible reading of James Clavell's Shogun (read it twice already but love the story) and "From Good to Great." I have some other audio books waiting for my attention but have been either too busy or too tired to work on the idea any further, but I do have some harry potter audio books I may give a listen to... I listen while driving, while working... in the bathroom... just about anywhere.
Device: Blackberry 8100 v126.96.36.199
Carrier: T-Mobile USA
Desktop OS: Fedora 7 Linux, Windows XP (vmware)