This is kind of neat. I was flipping through my wallet today when I stumbled upon a Where's Willy $20 bill. For those who don't know, Where's Willy is a program that tracks currency to show where a single bill has been. This perticular bill has come all the way from Vancouver BC since 2002.
The people who are doing this also have Where's George in the US. It's amazing how far a single bill can travel. Check it out for yourself.
Canada: www.whereswilly.com
USA: www.wheresgeorge.com