An old friend of mine got recently a GPS navigation device as a present for his birthday - such a tiny thing which you can carry while you are hiking or such. Comes along with some pretty usable hiking maps - really cool stuff.
Last time we met, he reported on his new hobby - geocaching. Pretty much the same thing like the "Schnitzeljagd" we are used to play a kids. Someone hides something which all the other try to find. Our days the location of the secret is posted on a dedicated website (see www.geocaching.com) and the whole community can try to find the secret. As a reward the happy finder of the secret get the honour of success by leaving a line in the logbook and reporting back the found in the community website. More detailed description can be found at wikipedia.
Sounds like a great opportunity to kill time and have a reason to explore areas you would never touch without a reason. As I'm not the proud owner of such a GPS navigation device - beside the car navigation which comes a little bit bulky. But in our days almost all the nice mobile phones come with a build-in GPS. I took my Vodafone H1 and pimped it with the vlkgps application. A little bit brittle and not that straight forward to use, but working. Might well be depending on the combinaten of the device and application.
All together it was great fun and we made a nice snow walk, but we think of improving the tooling. I'm thinking of getting a Android Phone anyway. This might be working better ....