S.E.
I use both paperbackswap.com and bookmooch.com. I think paperback is easier to use, but that's just me. They both work about the same, but PBS makes it easier for you by letting you print the mailing info out where BM just gives you the name and address to deal with on your own. They are both great sites and I make sure to keep my wish list active on both since my odds are higher that way :) Also, I have gotten some wonderful books for my son on the site - great for him to get "mail" and a book without a trip to the bookstore! :) Happy reading!