I just saw a video of Vijay Singh working out with his trainer, Joey Diovisalvi. It is a great example of a workout that has exercises in it that the average person wouldn't think a golfer would be doing. Aside from the typical things like medicine ball rotations and resistance band chop & lifts, Joey puts Vijay through agility drills utilizing an agility ladder, hurdles, lateral resistor bands and even the ocean.
Diovisalvi calls it "Movement Strength" as he is strengthening Vijay through all planes and ranges of motion on his dominant side and non-dominant side as well. A lot of people (trainers included) forget to work the body laterally. Lateral drills, whether they are with the ladder and hurdles, simple side lunges or even slide board work, help to strengthen the hips. Strong hips will help prevent to much movement in the backswing.
I agree with Joey's philosophy; he is training Vijay like an athlete because that's what he is. Check it out as it will give you ideas about some exercises to add to your workout.