BookMooch
Every time you give someone a book, you earn a point and can get any book you want from anyone else at BookMooch. Once you've read a book, you can keep it forever or put it back into BookMooch for someone else, as you wish.

There is no cost to join or use this web site: your only cost is mailing your books to others.

You receive a tenth-of-a-point for every book you type into our system, and one point each time you give a book away. In order to keep receiving books, you need to give away at least one book for every two you receive.

A different take on Book Crossings' "Catch and Release" program.

Share books you don't want, don't toss 'em in the trash or recycling bin!