Have you thought about buying or making a set of rings? You may be able to hang them in your garage, if you have one, or another high place, either indoors or out.
As has been mentioned before, rings are very versatile. They can be used for dips, pull-ups, push-ups and the much coveted muscle-up. And, they can be set up and taken down in minutes.
Check out http://www.ringtraining.com/
for more info.