hanging knee raises (dont swing, nice and slow, and squeeze your knees trying to touch your chest) 3 sets of 12-15
kneeling rope cable crunches (dont just pull the rope down towards the floor, curl it in towards your knees like a roll of newspaper) 3 sets of 12-15
db side bends (dont go to heavy or your obliques will get bigger and you wont see the v-taper in the abs, i use 25lb db, 30 reps each side)
some extra oblique work i like to do. broomstick twist sitting on a bench. 3 sets of 50 (25 each side)