I think that doing crunches with a 60-65lb. dumbell on your chest works the abs very well if you pause at the top and really squeeze for a count of two. Also, try grabbing the rope attachement (on tri pressdowns) and getting on your knees on top of a couple mats (piled on top of each other) and then using your abs to pull your head to the floor (tuck your hands - gripping the rope of course - behind your head). Again, squeeze at the bottom for 2 seconds. Hope that helped. Add in some ab machine work, some hanging leg raises, and some decline sit-ups and you've got a good ab workout.