LibriVox - free public domain audiobooks
OverDrive Media Console - Download eBooks and audiobooks from your library directly to your iPhone, iPad, and iPod Touch!
Audible - Audible is the world’s largest provider of premium audiobooks and spoken word content.
Listen Audiobook Player - Feature rich and easy to use player for your audio books.
Mobilism.org - A home for book lovers, app enthusiasts, and much more.
Libro.fm - A digital audiobook platform for independent bookstores