I've been told before and believe that training abs with weight is how you make them grow, it really just makes sense. I also bought and read a long time ago the Ultimate ABS book. In that book it said to do the lower abs before the uppers. I can't remember the reason but it had to do with the way in which the muscles of the upper and lower abs work together, and by doing them in that order you get the most out of the workout. Anyway my ab routine is as follows, if you have any suggestions or other exercises that work better let me know.
I start with 2 sets of hanging leg raises
I do the first 5 reps with legs straight and then
10 reps with legs bent regular knee-ups
Then I do 2 sets of 20 crunches with a ten pound plate behind
my head plus 10 reps of quarter sit ups with the same ten
pound plate.
Finally I do 2 sets on the ab ball with a ten pound plate.
I'm just getting back into it so I don't have a ton of sets or reps in me.
I start with 2 sets of hanging leg raises
I do the first 5 reps with legs straight and then
10 reps with legs bent regular knee-ups
Then I do 2 sets of 20 crunches with a ten pound plate behind
my head plus 10 reps of quarter sit ups with the same ten
pound plate.
Finally I do 2 sets on the ab ball with a ten pound plate.
I'm just getting back into it so I don't have a ton of sets or reps in me.