Hah, I had a quick look on a geocache website for any near me a while back and there were 4 or 5 within 1/2 mile of my house! I went and looked for one and found it after a while, cunningly hidden in a little hole in the ground with a stone over it. Not sure about apps or where you are located.
I think the Geocaching app is like like $10 (or was when I bought it) but it was definitely worth it. Otherwise, you can always just print some caches off of the Geocaching.com site and go hunt them with your GPS!
i've also very recently looked closer at the whole geocaching-idea and want to try it out, i never was geocaching but it sounds very interesting and funny as an motivation to "go out into the nature and move your body" ;o)
i hope i can find ones with my smartphone-gps because i cant really afford an 250€ gps at the moment, i have other plans with that money xD *looking at my lighting-shopping-list* xD