What Do You Do When You Get Out and Go?

Mr. B. at the top of Clawhammer Mountain in the Pisgah National Forest near Asheville, NC.   

What's something fun that you do that keeps you active and fit?
Many people do active things just because they are fun.  Write about your favorite activity that you love to do that is also good for you.  It can be a sport, a group activity, or even a job you do around the yard.
So what's your thing? Mountain biking? Basketball? Building a tree fort?