Here are some other free to use audio book sites for books that are no longer under copyright ..
http://librivox.org/
http://freeclassicaudiobooks.com/
http://www.gutenberg.org/
only those with speaker icon
I just did a search and also found the following, but I have not tried them ...
http://www.openculture.com/audible
http://www.booksshouldbefree.com/
only the public domain books are free
http://www.newfiction.com/
http://www.thoughtaudio.com/
http://www.podiobooks.com/
free, but they ask for donations
http://www.librophile.com/
not all books are free
http://www.learnoutloud.com/Free-Audio-Video
not all books are free
ttp://www.audiobooksforfree.com/