Follow the money.

• Position: Wheresgeorge.com helps tracking the Dollar bill movement - Brief article

Do you know where that crumpled dollar bill in your wallet has been? Dirk Brockmann, a physicist at the Max Planck Institute in Germany, might be able to tell you. Brockmann was looking for a way to track human travel, patterns--the paths people trace when moving around by foot, car, train, or plane. An American friend told him about Wheresgeorge.com, a popular Web site that tracks U.S. paper currency. Users enter the series and serial, numbers of bills along with their ZIP code. As more people do this, it creates a record of where each bill has traveled. And where the bills travel, so do people. Using data from the site...