I ordered this (after someone recommended this to me) :
http://www.15minutehell.com/
I will report back with conclusions. Anyway I would recommend you find a program in which the exercises are with body weight and not those that require you to go to the gym and life weights, it's very unnatural for the body to work with isolating muscle groups, and I read in some places it can even be less effective.
Also nutrition is super important, in order to get a six pack you must lose fat and burn more calories than you eat. Dietary fibers are very helpful with this.