Thanks to all who commented so far. Lots of idea were thrown around, from "don't waste your time" to puzzles to geocashing. I'll get to it this weekend, most likely with a simple QR code, brief explanations, and pointers to a few Web sites.
For reference, here's a couple of threads related to a problem along similar lines:
https://bitcointalk.org/index.php?topic=45881.0 https://bitcointalk.org/index.php?topic=45943.0and if it will do you any good, here's a link to some code I hacked out which takes lists of 'hashes' and forms them into sheets with 10 business-card sized things each to be printed.
https://github.com/tvghub/tvghub/tree/master/proj/bitcmp/trunk/print/pubI had some thoughts along the lines to develop a system which one could run multiple 'campaigns' either educational or commercial. The 'hash lists' would form the communications between the back-end machinery (where people go if the scan the QR or tap in the deliberately short URL) and the material handed out. This would facilitate dynamic value adjustments. And, again, avoid any need for a user to give any information about themselves.
I've lost interest in such a thing for the time being. The code was just hacked out enough to successfully get a few card sheets printed off then abandoned, but it might have some ideas you can use.