I'm developing a project to promote Bitcoins through the activity of Geocaching.
Geocaching is a real-world game of hiding caches near publicized GPS coordinates. Once the cache is found, people trade nik-naks and sign logs that they have been there. There are even GeoTags that can be moved around the world by Geocachers. The tags have serial #s that can be looked up and instructions will tell the Geocacher the tag owner's wishes and a log of the tag can be viewed online and followed to its destination.
Project Hidden Treasure is basically like the Bitcoin Faucet for the real world. Each week (or when someone finds my previous treasure), I'm donating a small amount of Bitcoins to an address, printing the private keys to the address on an informative Bitcoin flier, and leaving it in several different geocaches. The hope is that several Geocachers that come across the flier will be intrigued enough to understand the basic concepts of Bitcoins, follow the instructions to retrieve their free Bitcoins, and then share their experience with other Geocachers. The idea being that they will get excited about actually finding currency in their caches and spark their imagination like Bitcoin has already done to many of us.
If you would like to join me in this effort, let me know and I'll get you started to make your own version of a flier with your own private addresses so you can distribute your own fliers in caches local to you. I'd like to know how often you're putting new codes out so I can track them.
For more information, visit the project's home at: http://bitcoinintro.com/project-hidden-treasure/
Here is the flier template that Geocacher's will find: http://bitcoinintro.com/wp-content/uploads/HiddenTreasureFlier.pdf
Edit 2011-10-28: More info on Geocaching... http://www.geocaching.com/
I've already send them a request to accept Bitcoin. (so should you!)