There are a number of things you can do with resistance bands. Back in the late 60's a major training focus for pitchers was isometrics, building strength and speed thru resistance. A good article on isometrics can be found here: http://www.dryessis.com/wp/?p=39#more-39
You can find lots of info on resistance bands on the web, many isometrics can be done with no extra equiptment.
Hope this helps .... I should add that while on the isometric programs I never had any shoulder or elbow problems, and I never did any free weights for upper body. The only weight training I ever did was for the legs which is one area you really need to concentrate on, if your legs are weak you will develop arm problems.