Okay, this one I've had bookmarked for seems like ever. It's a site that you can track your US currency. The site is called Wheres George. You type in the serial number from whatever denomination of bill(s) that you have, spend it then track it. It's like the old game I remember playing when I was younger, you'd write some information on the bill, then spend it, and see if it EVER winds up back in your hands. I've entered four $1.00 bills and a $20.00. So it'll be fun to see where it travels and how far it goes.
So everyone get out your monies and pass the buck along.