I randomly stumbled across Geohashing when I was searching Wikipedia for Letterboxing and working out how it was different from Geocaching. There was a link to Geohashing at the bottom of the Wikipedia page, which in turn led me to the xkcd Geohashing cartoon, and hence to here.
I like the idea. Not sure I like it as much as finding actual physical things (a la Geocaching) but I do like the whole random nature of it, so maybe I'll give it a go. Sometime when the hash is realtively close - I don't like the idea of burning valuable fuel to go traipsing across the countryside for no real reason!