With BookMooch you can post the titles of books that you no longer need. Other BookMooch members will then let you know if they would like that title. According to founder John Buckman,

"BookMooch now has 70,000 members around the world, and people are joining at a rate of 300 a day. Participants create an inventory (the books they want to give away) and a wish list (the books they want to own). The *library* has some 500,000 titles.  I estimate that it will hit one million by the end of December 2008."

Two libraries currently using BookMooch are the Quezon City Public Library, Pasong Tamo (Philippines), and the Willow Creek Library in Willow Creek, CA. Buckman states that libraries will be a big focus for BookMooch in the next year.