Bootcamp
I have done it 4 times... 3 months in a row in 2006 and june 2007. It is a love/hate thing for me.
I loved it so much the 1st time I did it to more times. I lost a lot of inches. The first week is the worse, but if the group you are working with is good the workouts should be scheduled to deal with the soreness and fatigue.
Good luck.