http://librivox.org This is amazing. They have free audio available of most works in the public domain. The material is created by volunteers through the forums, with some works read by a single individual and some organized with different readers for each chapter. Everyone should check out their catalog. Going to listen to so many books on my road trip :) I'll probably fill up my external hard drive with 250 gigs of books and then be able to move to my computer & then to my iPod to play on the car's radio. Plus I can listen to books while playing poker (probably need to play a couple less tables and pause the audio incessantly to actually pay attention).
I think I'll start with Notes from Underground (though I have read that before, ages ago), and then I think On the Origin of Species (a whopping 24+ hours of audio).