Next to metal detecting Geocaching is one of my favorite activities. especially with the family.
Go to Geocaching.com,register, put in your zip code and you will be surprised how many cache's there are around you.http://geocaching.com
I have been out twice with a car GPS and did not find any thing I am going to try a model without car directions that is made for hiking, and this time bring a compass and hope I have better luck. My son is interested in this.
Another awsome outdoor activity---the kids love it----geocaching.com is the place to start....and any GPS will work--I've been using a $99 magellan for years and it can usually walk me right up near the cache--and the number of caches out there is amazing---i live in a very rural area and there are proabably 300 caches within an hour of the house.