I once torrented an audiobook that I couldn't find online. Turns out it was because it had not been professionally read yet but had a few uploads from some people. Apparently, there is a fairly large number of people that record their readings and then upload them for others.
I was pretty excited until I realized I couldn't make it through the one I had downloaded due to the guy's crazy whistling S and his frequent blud-blud-blundering of words.
Holy crap was it terrible...
I tried 3 more of the non professional recordings from different people before i realized that having the ability to read aloud (well) is actually a rare gift. I just assumed that, since I have it, everyone else does. Sadly, not the case!
I'll be paying for any audiobooks I get from now on.
Now.... To answer adriley's question.
I have no idea. I'm just going to stick with Amazon.
http://librivox.org/ has a pretty good selection of free audiobooks from the public domain. They're all read by volunteers though, so the quality is all over the map.