Sherry try a free one to see if you will like it. Yes you can get the best sellers and all the current ones.
Here's a couple of websites I just pulled up. I haven't used it so I don't know anything about them - but worth checking out.
Free Audio Books - Download an audio book in mp3 or iPod format today!
AudioBooksForFree.com
Robot Unicorn Attack sounds like one I would like!