Smelt, my family and I have been Geocaching for about 6 months now. When we travel for anything we usually stop to find a few caches along the way. The kids ages, 20, 17 and 12 really enjoy it. They really enjoy the ones that take a little detective work and problem solving skills to find. I usually don't like to give up the time from fishing but it keeps the kids and wife happy to spend an hour caching. Additionally, I occasionally go out with just one of the kids for some one-on-one quality time. We really enjoy that. We get great exercise and have some great talks. The kids love it when they find the cache before I do, especially the youngest. As an added bonus it has motivated us to visit some real pretty and interesting areas that we might not of otherwise, Its amazing how many great trails and parks there are that we have gone by dozen of times without ever enjoying them.
So in a nutshell, its a great family or individual activity and there are some people who are almost as fanatic about caching as I am about fishing.
Let me know how you enjoy it.
Dan
(aka 4walls on geocache.com)