P90X is a series of 12 workouts from BeachBody (
www.beachbody.com ) that has strength workouts, a plyometrics workout, a yoga workout, a stretch workout, and a cardio workout. The workouts come with a guide that takes you through a 90-day rotation following 1 of 3 programs.
I think it is very different from Cathe in that it allows you to lift heavy for fewer reps or lighter for more reps, follow your own pace for many of the exercises and is set up in either superset fashion (alternating opposing muscle groups) or in a cyclical fashion (doing one exercise for shoulders, then triceps, then biceps, then repeating then having a stretch break).
If you've done Cathe's weight work, P90X will take you to the next level.
If you search for P90X on this site, you'll find several threads that will give you more information.