I recently reminded myself of a fun website. This is a completely unasked for plug by the way. If you have read a book, and are done with it, then this is a cool idea. Rather than leaving the book on your bookshelf to pine away, send it out into the world to be read by someone else. All you have to do is register, then register your book (entering the ISBN code is pretty much all it takes). You can leave a comment about the book if you like, and then you leave the book somewhere, and note on the website where you left it (you can be as general or specific as you want). You leave a note in the book with the website and registration number.
Then hopefully someone finds the book, goes to the website, and registers that they have the book. The idea is to keep sending the books out over and over again so that your book travels around the world. You can also use the site to find books too. If you live in a big city then this has the potential to be a lot of fun. I don't, so I haven't done much with it so far. I have released 2 books so far though. One book seems to have disappeared into the mist. The other I just released recently and I'm still waiting to see if someone finds it etc.