I did a little Geo Caching a few years back. It was a lot of fun. I just used the GPS and Google Maps on my HTC Mogul at the time. I visited a lot of the local caches and just never got around to going back out. Some of them can be hard to find given the clues on the Geocache sites.

I like the Geobomb thing. I guess it would have to be in an area with a few Geo Caching BOTL's for it too work though.