It's summer! With the summer comes the time where there's more to do for cheap or even free. Of course, every state is different. I'm from NM and can't say it's very budget AND activity friendly. There's a lot to do to keep you active and even outdoors, but everything costs. With tough economical times and, for me, a very limited income, it's simply not feasible to go to waterparks or amusement parks regularly. We've turned our attention, once again, to the cheap or, better yet, free activities. Outdoor markets where fresh produce and live music is a great place to go for your produce shopping and walking around. Not only are you getting in some exercise but you're also supporting your local farmers.
On another note, many places seem to be pushing for more familial outdoor activities, creating bike trails and having weekly free events that take place outdoors or in large convention centers. We have free local bands playing weekly and it's fun to get up and dance with the kiddos or relax with friends to jam out.
Parks are also becoming cleaner and safer, so even if you don't have children you can go for walks. If you do have kids, you can easily join them on the swings and see who can swing higher the fastest.
Google summer events for your location and you'll probably be amazed at what you find. So go out and enjoy yourself.