Hi clubm,
You asked about audio books, well if I buy them I get them from ebay or half.com, but now I just swap them. I get them from paperbackswap.com. Join them and you can swap books, audio's and they even have a DVD swap. You only pay the postage to send books/audio to someone else. If its the same as when I joined they start you out with a few free books when you add your own books or audios to the list to swap. I've been a member for several years, its great.
Here is a link that might be useful: swap books
jannie
clubm