Abs work out using ab roller

(you know the equiptment I mean-its like a metal frame that is like a circle that supports your neck whilst doing crunches)

I have one of these.....does anyone have any guidance on a really good workout with them. I want to work damn hard on it as I have my holiday coming up.

Tips and links to sites warmly welcomed.

(any idea on how many calories it burns too)

THANKS xxxxx