There's a lot of workouts that hit your abs in one way or another, but as was said if you're trying to see the definition of your abs, all the sit ups and crunches in the world won't show your progress if there's still fat covering your abs. Lower your body fat % and do things that target your abs along with other workouts, like planks, abdominal hold, mountain climbers, etc.
Just do abs if you have time... I usually just do a set of dragonflies at the end of my workout if I'm feeling like it. My body fat's probably around 16%, so I can barely see my abs (just upper abs/obliques)... kinda sucks working them when you can't see it. A strong core comes from deeds and squats though.
My current chest workout is:
Dumbell incline (superset with incline flies)
Flat barbell bench
Straight-arm pull-overs (hits tris, but if you stretch far enough it's good for upper chest)
Cable cross (with drop-set or double-drop if I'm up for it)
Low weight, high-volume flat dumbbell bench (superset with flat flies)
I'm playing around with it a lot, but so far I find drop sets and supersets to be pretty killer.