If your quads are much larger in relation to your hamstrings, and you want better proportion, try any of the exercises listed above, as they can all target hamstrings. You should also decide if you want to lay off of quad dominant exercises for a while in order to allow your hamstrings to catch up. That's a very difficult thing to do, but I have personally taken 6 months off of direct training of specific muscles in order to better my proportion and it worked great for me. Your quads will still get a lot of stimulus from any leg exercises you do, aside from hamstring curls and stiff legged DL. Any type of squat or press will still utilize some of your quad