Awhile back, Inside The Net had the creator of BookMooch on their podcast. I really enjoy using BookMooch. I have an account on there and also at PaperBackSwap. For the most part, both sites are wonderful and a good way to get rid of books I do not want. I have scored some weird and very interesting books via BookMooch. There are a few authors I always search for when I have a credit and I have been able to acquire some great books.