Just to get things started, take a look at one of my all time favorite resources:
Here's the sich ... 1. You post books you don't want anymore. 2. Other swappers look at your "bookshelf" of available titles, and choose what they want to receive from you. 3. For every one of your books someone else requests, you receive a credit. 4. YOU may cash in the credit by choosing a book on someone else's bookshelf. 5. You pay for postage to send requested books to others (usually about $2.50), and other swappers must pay for postage to send books you request.