Unfortunately, it's impossible to spot-reduce. I know exactly what area you're speaking about - I have had the same problem myself. (At this point, according to my PS, it's mostly skin in my case).
I'd do chest workouts - presses and flyes of various types and at various positions (seated, incline, flat on your back - check the ABC Bodybuilding site for lots of different exercises). But even MORE importantly - check your diet - if that's fat, then you need to make sure you're eating clean so you can burn off that fat.
Hope that helps