How about..
-Make a stamp to stamp QR codes and/or urls on bills.
-Create priv keys from the bill's serial number (by sha256 etc)
-Transfer smallish amounts do dozens, hundreds of such stamped bills
-Website where the QR/url points to lets you directly enter the bill's serial number and the state you live in, lets you redeem the bitcoins and explains what this is all about
-Extra points for making this big and viral!
This is an very cool idea! Here are some rules for a potential game along these lines.
Rules for a BitCoin "BlockChain Letter" GameCreate a website and work it like "Feed-Ze-Birds". People that are interested in promoting bitcoin can donate BTC to the website to "prime the pump".
1) Player obtains a dollar bill with a "Bitcoin Blockchain Letter" website address on it.
2) He goes to the website to see what it is all about. If he is interested in playing, he logs in and specifies the serial # of the dollar bill that he encountered.
3) Player writes web site address on any number of dollar bills and notes the serial numbers of each.
4) Players then registers the serial numbers of the dollar bills he tagged, and provides a password for each. (The password can be the same for all of the bills he registers,but it doesn't have to be). The site remembers both the passwords and the serial numbers. Each dollar bill can be registered only once.
5) The combination of password + serial number is used to generate a public/private key bitcoin address, which the website provides to the player. So, only the site itself and the initial registree have the information necessary to obtain any bitcoins associated with that address.
6) Once per month, all BTC are collected from all registered addresses. (This is to keep the bitcoins from being permanenly lost for no good reason). These collected bitcoins, along with any new donations, are spread out evenly across all registered bills.
7) When a players finally "gets the point" of bitcoin, they are encouraged to donate 1 BTC to each of 10 bills further up the chain of registered bills. This will indirectly "prime the pump" if they are not collected by the end of the month by the person that initially registered them.