One thing, though, you must realize, abs are dependent more or less on your amount of bodyfat, not how big the muscles are. You generally need like 5-10% bodyfat to see abs. You'd have to get them really huge to poke out through a lot of bodyfat. If you just add muscle while keeping the same amount of bodyfat, you'll just get more of a belly, as exercise can't really "spot tone" fat away, it just all comes off randomly.
Also, while training the abs is good, if you do too much front abdominal work, without working you obliques, and back muscles, you can actually screw up your posture, as your front abdominal muscles will overpower the rest of your core and back muscles. I mean it's sorta rare, as most people won't do enough ab exercises like that to do that, but yeah. The other thing too, your abs purpose is a stabilizer muscle. They're there to keep your body together, more or less. So, any activity involving your whole body, ie, skating (my favorite), running, weight lifting, will improve your abs, just over time, not instantly.