I came across Audiobook Jukebox recently. This site is a compilation of people who give concise reviews of what they have recently heard. The list of reviewers is extensive (take a look over at the main page under the "reviewer sites" gadget on the right hand side) where the beginning page snip begins with numbers and the letter "A":
On Ravelry, several forums have quick recommendations about favored audio books. Go here or here to see what the knitters of the world are putting in their ears. It's fun to learn what others are enjoying on audio.
Once you have determined the new book you want to hear, several sites are available for downloading that book, or poem, or short story. There is your local library, of course, which should have the OverDrive media console where you can download your mp3 books. You first need to download the interface between your library and your computer, but then you are good to go. Although recently I have had a problem with a very long download time required to put all the sections of the audio not only into my library, and then also transferring them to the iPod. This is a new problem that I hope the innertubes...err..internet gurus, get rectified soon. ( I got so frustrated last week trying to get The Paris Wife (Paula McClain) into my media files that I finally gave up after numerous attempts over four days.)
But I digress. Back to obtaining your audio books. Not only will your local library have a wealth of titles, but also LibriVox is a tremendous site for free downloads. LibriVox provides books from the public domain, and are generally read by volunteers, not professional voices. LibriVox also has a podcast you can access from here.
From "free" to "for-purchase": Amazon has just a few, comparatively speaking, of mp3 audio book downloads. iTunes has a more comprehensive listing. But Audible is the real winner for absolute quantity and quality of available audio books. Downside: you might get your first book free, but you will need to sign up for continuing books available monthly for a fee you might not want to commit to.
And what I recently purchased but have not yet listened to is through a recommendation from the moderator of this forum, who recommended Dorothy L. Sayers as an author. The book is The Unpleasantness at the Belonna Club. Email me if you want a quick review of this book (nmccarroll at Q dot com).