Al, search on the internet for exercises called "internal rotation" and "external rotation". These are exercise that are usually performed with those rubber bands attached to a stationary object. They work wonderfully and is what I've been using since hurting my shoulder at work.
You could also try to find a book called "Core Performance". It focuses on unstable exercises for all parts of your body. It makes you stronger and more stable in your hips, knees, lower back, core, shoulders, etc... It does all this without adding much muscle mass, so you stay strong and flexible. Great book, just don't let all the mumbo jumbo overwhelm you, read it through once or twice and the routines won't look so intimidating...Mike