Two interesting site I read about today from Darryl my good friend....
Where's George
BookCrossing
Similar concept, I like BookCrossing better. The idea is that you read a book, tag it with a BookCrossing number, and then give it away, donate it, whatever... then at some point in the future, when someone else reads the book, and discovers the book crossing number, they can goto www.bookcrossing.com and register the book, and you can see where your book ended up.

wheregeorge is the similar idea, using serial numbers on money bills.

Cool idea, kinda like when we were kids, and we attached these post cards to balloons and let them go to see where they end up and get mailed back from.... interesting concept.

That reminds me, if you haven't seen "Pay It Forward" the movie, go see it. :-)
john