What exercise is good for rotator cuff rehabilitation?

Exercise in the water - water provides a supportive environment that creates space in the shoulder joint and at the same time offers a level of resistance that helps to strengthen the small shoulder stabilizer muscles. More specifically, an aqua yoga practice will offer someone rehabilitating from a rotator cuff injury the opportunity to practice a combination of mindful weight-bearing (like side plank pose at the pool wall or pool steps) with mobility movements.

Well that's a good question. Depends upon the injury, and it's severity. I am big fan of conscious mindful movement. Combo of range of motion and stabilization in equal measures. Take a minimalist approach, especially if the injury is recent, or severe. Pair breath and movement. Be patient with the process, as you heal the connective tissues.

If you're sure it's not torn, "pendulum" exercises can keep the joint healthy (lean forward onto a counter and let the arm hang, swinging it easily and naturally in each direction). To keep the muscles healthy, use VERY LIGHT weights for rotation work. Start with your upper arm close to your body and rotate in front of you. Do not increase weight, increase reps. You are building endurance, not strength. For more advanced exercises, see an MT, PT, or OT to make sure you work the muscles that are problematic.