I struggled with getting enough exercise, too. Now I do the http://www.startbodyweight.com/ routine three times a week. It really makes a big difference in just three hours. You don't have to go to the gym or buy fancy equipment, either. All you need is a pull up bar and a pair of gymnastic rings.

The biggest benefit for me is making my back much stronger. I used to throw my back out several times a year just from doing normal stuff like stacking firewood. Now I'm much more resilient.