What are some good excercises to help rehabilitate a broken hip?

The appropriate type of exercises for  a broken hip depend much upon what stage of recovery you are in. First, I would recommend seeking the help of a physical therapist who can give you therapeutically appropriate exercises to meet your specific needs. But that being said, there are some basic themes that hold true in rehabing a broken hip--whether it has been pinned or replaced. In general, one wants  to focus on strengthening the hip extensors and abductors which are the muscles on the back and outside part of the hip. These muscles provide stability and power for the hip which is needed for walking, getting up from a chair, and climbing stairs. So some simple ideas are walking forwards, backwards, and sideways in waist deep water to get resistance on the muscles. An upright or recumbant bike is also an excellent form of exercise to strengthen the hips. Finally, just doing simple sit to stand exercises from a standard, firm chair in a slow and controlled manner with as little hand support as necessary for balance will help strengthen the gluteal muscles. This is a start to your road to recovery!