What are good physical therapy exercises after a shoulder dislocation?

Before beginning. .. Before beginning rehab for a shoulder dislocation, you should be evaluated (minimum of exam and x-rays by a qualified physician) to rule out injuries, such as a fracture, that require early surgical intervention. If cleared, a rehab program, including scapulothoracic stabilization and balanced rotator cuff strengthening, under the guidance of a pt or atc may be safely instituted and progressed.
Isometrics. There are basically two components of what stabilizes a joint: static & dynamic. Static issues that you can't really strengthen include ligaments/cartilage/labrum/etc and negative (suction) pressure between the joint. Dynamic stabilizers (which you can strengthen) are the muscles around the joint. Proper muscle strengthening surrounding the joint can definitely aid in joint stability. See a pt.