Bridges, side bridges, russian twists, full range-of-motion crunches on a balance ball, hanging leg raises. Use two exercises per session, do them thrice a week, coupled with heavy deadlifting, squatting, and overhead pressing. You'll be fine.
I made a sweet bench I call the ab rippa out of 4x4s. It can handle up to 200 lbs if you can pull it. I hurt my back a few times and I'm kinda limited. It works better than any ab excersize I've tried so far. I might of stumbled on to something..maybe I should patent it and give ******* a call
the only guys doing ab crunches on the swiss ball where I train are the private trainers, never a serious strength athlete/bodybuilder/PLr...etc. If you have to use equipment, try the roman chair.