BookCrossing is a fun way to get rid of those books you bought, read, and want to get rid of.
You register your book on the site, then print a label or write a note with a unique number on it to explain what's going on. Then release it! Leave it on a bench, at a playground, the mall, anywhere another reader might find it. You could even donate it to the library.
When someone finds it, they follow the instructions on the label to let the website, and you, know who got it and where it's headed.
If you're younger than 13, you'll need a parent to register on the site with you.