There are a number of other sites that offer free audiobooks. Many of these audiobooks are of works that are in the public domain. You won't find the hottest best sellers or many new books on these lists, but some of these sites do have fairly extensive collections, often in multiple languages. Many also offer downloads in multiple formats.
Project Gutenberg (http://www.gutenberg.org/browse/categories/1): Project Gutenberg was the first on the block offering digitized text for books in the public domain. They have an extensive collection and more of their books are read by human voices. They also provide books in many other languages! Also available as an app: Gutenberg Project
LibriVox (http://librivox.org): LibriVox’s objective is “to make all books in the public domain available, for free, in audio format on the internet.” Books are read by human voices (you can volunteer to read!) and can be listened to through your browser, downloaded to your iPods or other mobile device, or burned onto a CD. LibriVox is a non-commercial, non-profit and ad-free project. Also available as an app: LibriVox Audio Books
Lit2Go (http://etc.usf.edu/lit2go/) - Lit2Go is a free online collection of stories and poems in Mp3 (audiobook) format. An abstract, citation, playing time, and word count are given for each of the passages. Many of the passages also have a related reading strategy identified. Each reading passage can also be downloaded as a PDF and printed for use as a read-along or as supplemental reading material for your classroom. This collection of children's literature is a part of the Educational Technology Clearinghouse.
Classic Poetry Aloud (http://classicpoetryaloud.podomatic.com/): “Classic Poetry Aloud gives voice to poetry through podcast recordings of the great poems of the past. Our library of poems is intended as a resource for anyone interested in reading and listening to poetry. For us, it's all about the listening, and how hearing a poem can make it more accessible, as well as heightening its emotional impact.”
ejunto (http://www.ejunto.org/): The name comes from Benjamin Franklin's literary club called The Junto. Franklin formed his club for the "mutual improvement" of his members. The Junto was free, fun, and educational. Our website shares that mission. We offer historical and philosophical mp3 audio books in the public domain for direct download including the U.S. Constitution, The Declaration of Independence, The Autobiography of Benjamin Frankline, Plato, Machiavelli, Marx, and more!
LoudLit (http://www.loudlit.org/) Literature for your eyes and ears. May listen and read on the web or download as mp3.
Loyal Books (http://www.loyalbooks.com/) - The website and app give you access to thousands of audiobooks organized into dozens of genres. Stream the books instantly or download them for listening offline. Stories are available in over 25 languages! With variable speed playback you can slow down books to learn new languages or speed them up to enjoy even more material on your reading break. Also available as an app: Loyal Books
Online Audio Stories (http://www.onlineaudiostories.com/): Books may be downloaded. Online Audio Stories was created by Abigail Rice, a professional actress and writer. Geared to children. Also available as an app: Stories Aloud
Open Culture (http://www.openculture.com/freeaudiobooks): Download hundreds of free audio books, mostly classics, to your MP3 player or computer. You’ll find great works of fiction, poetry and non-fiction, by such authors as Twain, Tolstoy, Hemingway, Orwell, Vonnegut, Nietzsche, Austen, Shakespeare, Asimov, HG Wells & more. In addition to audio books, Open culture provides access to free online courses, free movies, free language lessons, free ebooks and other enriching content. Also available as an app: Open Culture
Storynory (http://storynory.com/): Storynory's actors read myths, fairy tales, and original series. Stories can be easily downloaded as audio files. New books added weekly. Geared to children.
ThoughtAudio (http://www.thoughtaudio.com/): ThoughtAudio offers “free audio books for a selection of classic literature and philosophy titles. Click a title to access the audio and pdf document.”
In addition to these sites, don't forget to check out your local public library (http://www.cambridgema.gov/cpl) for access to local and statewide audio resources!