Jacob's "Especially the lifeline products (rubber bands) in the second post might be a good match" would be a good way to go. You could probably work everything that way and they probably come with instructions on how to use them for the muscles you want to target.
I would imagine you could wrap them over your arm (over the tricep next to your elbows) to keep tension off the elbow joint and work your shoulder muscles. Something similar could be done for chest muscles.
I also like akratics resistance pull up. You start in the up position and try to keep yourself from going to the down. If you do 10-20 of these 1-3 times a week you should eventually work up to being able to do actual pull ups. Another option, you could try a low bar and assist yourself minimally using your legs. I am a firm believer that pull ups are one of the most useful upper body exercises. They work many muscles,big groups like lats, and even increase your grip and forearm strength. I just hope you don't have problems as it might transfer too much stress through the elbows in your situation.
Let us know how an attempt at a pull up feels!