One of my weakest areas is my core. I know I haven't been posting my core work outs but I have been more diligent and doing them. I usually work my core muscles separately from my powerlifting training. Twice a week I do a variety of core strengthening exercises. Tonight went like this.
High Crunches - 3 sets/20 reps.
Lying Leg Raises - 3 sets/20 reps.
Lying Leg Twists - 3 sets/20 reps.
After this my abs and obliques feel quite tight. Keeping up the core work will do nothing but help my lifts.