The Guardian Unlimited offers an overview of digital audio book sources.
You’ve loaded your CDs in to your iPod, you’ve assembled playlists and discovered the joys of shuffle mode. But the first flush of gadget love is fading. What can you do to re-kindle the affair? Why not experiment with digital audio books? There are several obvious advantages. With books on tape/CD, you’re often juggling several cassettes or discs. In contrast, an unabridged doorstopper by Tolstoy fits easily on an MP3 player/iPod, with space for more. And thanks to electronic book marking, you can keep your place on several digital audio books at once.
(Link thanks to Maud Newton.)