I'm often asked what the best exercise for abs is and there's a long answer and a short answer. I'll save the long answer for another time and get right to what most people want to know when they ask for the best abs exercise. People usually want something they can feel right away. One of the best abs exercise s I know that you will feel working immediately is the spin crunch. Most people I have shown it to have a love hate relationship with it. They hate it because it's difficult, it burns, and it looks as silly as a clown in a courtroom. But they also love it because they know it's working. If you've done the Fat X program then you know the spin crunch, if you're knew to it and want to check it out it's demonstrated in Fat X workout video Day 3.
The nice thing about the spin crunch is that you can make it more difficult by doing more spins and or holding weight while you perform the spin crunch. Give it a try and get those abs burning.