You can't spot reduce fat. THe only thing to do is to work on burning/losing it, and your body decides where it will come from. For me, my belly is stubbornly hanging on. I've lost 37 pounds and dropped 4, almost 5 sizes from a 12-ish to a 6, 4 in some items. But, my belly is still hanging around. I figure/hope the last 10-15 pounds will come from there.
To work the muscles, try doing a different variety of ab workouts to get them back into shape. Make sure to work the lower as well as regular crunches. I like reverse crunches a lot. Pilates and Yoga have some very good core moves as well. You may want to check out a class or video or maybe work with a trainer for a few sessions to get some ideas.