Originally Posted by Corporate Thug
Look into insanity. It's really a terrific workout. I'm did a few sessions and I was drenched after each workout. Each session is about 45 minutes long. I would say about 10 minutes or so goes to stretching exercise and rest in between sets. It does a good job of giving you a full body workout without using any equipment whatsoever.
I really would have loved to stick with it but it was way too painful on my previously fractured foot w/ torn ligaments.
I wouldn't exactly call 45min quick. Overall, I think Insanity requires a lot more building-up than it suggests. I think utilizing body weight movements in a circuit-like fashion is usually pretty effective and fast. For example:
5 rounds of:
20 air squats
Probably won't take you more than 15min to complete, but you work in upper body pushing, upper body pulling, lower body, plyometrics a bit, etc. I've always fancied thought kinds of workouts when I'm low on time. Still gotta warm up beforehand (at least 5min) though.