I know Where's George is sooo 1998, but 10 years later, it's captured my imagination like nobody's business.
The idea is simple: Each dollar bill has a unique identifier on it, and were you to enter them into a database, and track instances of a dollar bill's possession, you could monitor its travel throughout the world.
For the last few weeks, I've been religiously stamping my dollars -- $1 bills only; it's George for a reason, Media Dieticians -- with a stamp purchased from Holmes Stamp & Sign and releasing them back into the wild.
All my dollars have been virgins -- no previous entries, these -- but my sense of money and how money moves has been heightened.
Where does your money go? It's not that difficult to tell.