Apple Computers don't do many things for free (or even allow you to access free things), but the podcasts category on their itunes store is an honorable exception. Within the podcasts are a subset of audio books recorded by an organisation called Librivox. This non commercial project uses volunteer readers to voice classic books in the public domain. As you would expect, the quality of recordings is variable. Hundreds of books have been recorded, and all comers are welcome to contribute. Audio books are also downloadable directly from their website. Overall, a very worthwhile project.