Here is a tough one for you. Abs Accumulator is a 20 minute Abs Session. Give it a try and let me know how you get on. I love the intensity of the accumulator set up.
Basically you have a number of exercises. You start at exercise 1. You then do 1 again plus 2. Then 1 plus 2 plus 3. Then 1 plus 2 plus 3 plus 4 and so on all the way through until you do all of your planned exercises.
It can be very intensive and a great way to get a sweat on.