I'll be honest, and say I learned about it from a comic book... The Knights of the Dinner Table, to be exact.
I didn't even have a clue that a hobby like geocaching existed, until it was mentionned in an editorial in the comic book. Since then, I've logged two caches within 2 weeks of getting a GPS, and I've assembled the items for a cache I'll be hiding tomorrow.... that's filled with Tim Horton's collectible stuff, for all you coffee junkies out there.
So how did everyone else here find out about geocaching?
Sigrun.