Posting this from BB.com. I think it's good stuff:
http://www.bodybuilding.com/fun/dorian1.htm
and:
You need to mainly strengthen 2 muscles in the rotator cuff: the supraspinatus and infraspinatus. Use front lateral raises and my exercise #1 to hit the supraspinatus and use external rotations and my exercise #2 to hit the infraspinatus. See these links for instructions. Remember light weights, slow smooth movements, and perfect form or you'll re-injure yourself very easily.
http://www.exrx.net/WeightExercises...teralRaise.html
http://www.exrx.net/WeightExercises...alRotation.html
I also suggest these shoulder stabilization exercises for variety:
#1 (supraspinatus). Hold your arms out to your sides with your elbows bent 90 degrees, forearms to the front, palms down -- as if you were getting ready to row. Do one arm at a time. Take a *LIGHT* dumbell (this exercise is much harder to do than you think it is first time especially when rehabbing a supraspinatus injury... try 5 lb DB's first set to get the form right, 8 lb dumbells max first week) in your hand and keeping your upper arm fixed and parallel to the ground and the arm bent at 90deg, swing/rotate the dumbell *slowly* up to vertical in a smooth arc so that it's about 6 inches away from your ear. Let it rotate back down *slowly* through the same arc in a fixed plane until your forearm is parallel to the floor. Emphasize perfect form and *light* weight to prevent re-injury. If you can't do 15 reps without the burn, the weight is too heavy.
#2 (infraspinatus). Same concept, different direction of rotation. Lie on your back with your arms out to the side, elbows bent 90 deg, palms facing up as if you were steamrolled into the ground. Pick up a light dumbell in one hand and keeping your upper arm fixed out to the side and your elbow bent 90 deg, rotate the dumbell up in a smooth arc until it is vertical, your forearm perpendicular to the ground. Let it back down slowly through the arc until your arm is parallel to the floor. Repeat. Again, light weight, perfect form, 15 reps.