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Book Swapping

I think it should be an international site.
I've forgotten what it's called, but it's really quite popular. The first time I heard about it was on TIME magazine I think.

It's a site where people can register to and list a book they'd like to share.
The book will then be given a page* on the site, and you'll be given something to print to stick on the insaide of the book that encourages the next reader to go onto the site, get onto the book's page* and write a review about it. Then she passes the book on and the next person does the same thing and so on. And you get to check the progress of... BOOK CROSSING!!!
Oh My God.
Yes!!

I'm typing this half-way and it comes to me!
It's BOOK CROSSING!
I was thinking about it for nearly half and hour and trying to source it on Google...
*jumps around madly*

Book Crossing