You could always use your door for pull ups! If the door is sturdy enough, just open it up and shove a shim, book, or towel under the side furthest from the hinges. This will increase the structural stability of the door and keep it from damaging the hinges. Now grab the door and start banging out pull ups! Or you could always use a suspension trainer like The Life Line Jungle Gym (Fitness Equipment) and use that on a closed door. The jungle gym would also double as a tool for push ups, dips, rows, tuck knees and a whole lot more if your looking for something for more than just pull ups. And it's 1/3 of the price of every other suspension trainer out there.
Fitness Is A Journey, Not A Destination.