Why insanity in particular? The reason I ask is there are a lot of options out there so I was wondering whether there was something specific you were looking for. There is a 8 week program that people on another forum described as like a lighter "insanity". I don't know how true it is since I don't have Insanity, but it is a pretty solid circuit of body weight exercises and it also gets my heart rate up. It is called Weider X-Factor ST. The program is 8 workouts that you are meant to do 3 times a week, they get progressively harder each week. The intention is that you do cardio on the off days. It comes with a few bonus workouts including a more challenging body weight workout that can extend it to 9 weeks, but I really didn't like the instruction on the bonus workouts (it had a different instructor). I would say this set is good for an intermediate level of fitness, but it can be as challenging as you want to make it. Here is the link on Amazon, www.amazon.com/Weider-X-Factor-St/dp/B0055
Another option that is free, have you looked at the workouts on bodyrock.tv?