Favorite exercise?

Push-up's, dips, and pull-up's for upper body strength... if you don't have a bar for dips/pull-up's there should be something you can improvise with.

Planks, sit-ups, supermans, and oblique crunches for core strength.

Body weight squats, lunges, and step-up's for lower body strength.



Mix this in with cardio (running distance or intervals) and you should be able to maintain a relatively high level of fitness.



Resistance bands are great as well like Cooter said. I don't personally use them, but have friends who are fitness freaks who swear by them and have produced results with them.