Check out this odd little site, "Where's George", especially for people with time on their hands. People enter in the serial number of a dollar bill, and the site tries to track it's travel through the country. The power of the net.
Interestingly, in this (and several other) article, they say that using the patterns detected by Where's George (they call it a game) scientists actually have learned useful new things about the spread of infectious diseases in the USA, a very "au courant" topic.
"We were confident that we could learn a lot from the data collected at the www.wheresgeorge.com bill-tracking website, but the results turned out far beyond our expectations," said Lars Hufnagel, a post-doctoral fellow at the Kavli Institute for Theoretical Physics at the University of California, Santa Barbara and co-author of an article describing the research in the January 26 issue of the journal Nature" (from Science Blog)
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