Geocaching
One of my hobbies is Geocaching. It has become immensely popular over the last few years. I wouldn’t categorize myself as an avid geocacher, but it is a great excuse to get outdoors. Geocaching is a treasure hunting game in which boxes of trinkets, logs, etc are left in various locations about the planet. The exact coordinates to the particular item, or “cache”, is published on the website with any particular additional information that might be needed to find the item.
You then use your GPS to locate the item. When you find the item, you sign a logbook, and log your find on the website. Some folks have over 10,000 finds. As I type this, I have 32 finds. 
If you love the outdoors, nature, the sunshine, and don’t mind getting a bit of exercise, its a great hobby. Another advantage is that it is completely free (save for buying a GPS). There aren’t many other hobbies – especially aviation – that you can say that about.
Checkout the Official Geocaching Website
My screen name is: bryrisjs