A
website,
www.wheresgeorge.com, devoted to tracking the location and condition of
American dollar bills of all commonly-used
denominations as they travel throughout the country.
In order to use Where's George, a person enters the denomination, serial number, and series (date) of a bill, his local zip code, as well as optional notes on its condition and where it was obtained, into spaces on the webpage. The person then marks the bill with Where's George's URL, either by writing it along the border in pen or using a rubber stamp, and spends it. It is up to the next person or persons to have the bill to repeat the process.
Where's George came under government scrutiny shortly after its inception for selling rubber stamps with which to mark the currency. It is against the law to deface currency in a manner that would make it impossible to spend or reissue, though whether a simple rubber stamping would constitute such defacement is questionable. Where's George has since stopped selling rubber stamps, however.
A similar tracking site for Canadian currency is called "Where's Willy". Also similar is BookCrossing, which uses the same principles for tracking literature.