There are several places where one can get free audio books. It’s great to listen to on the road, waiting on the bus etc. It’s also a great tip for people with insomnia problems. I sometimes aren’t able to sleep all night, and the feeling of desperation because I don’t get the sleep I need is not fun. That’s one of the moments where I understand why people become drug addicts. Just anything than the state I’m at, in that particular moment. I think the reason why audio books works so great for me is that they are not in my language, and because I think in images. Everything I hear, I see (which is why I can become nauseous when somebody tells me in details about when they broke their legs etc).
Librivox provides free audiobooks from the public domain (the copyright has expired). You can also volunteer to read in books if you’d like.
Manybooks have also a large collection of audio books. At the moment of writing this post, they had 838 audio books available.