At Home Workouts

Even if you don't have access to a gym or don't have time to go to the gym, you can still get a great full-body ass-kicking workout in right at home. We always did circuit training as a form of conditioning at Stanford and most of the stations didn't involve any equipment. Here's a quick 20-minute workout (minus warm up and cool down) that's sure to have you sweating in no time:

[be sure to stretch and warm up beforehand]
Do each exercise as many times as you can for 1 minute. Keep a timer running and rest when needed but jump back in as soon as possible.

Suicides
Squats
Lunges
Jumping Jacks
High Knees
Push Ups
Mountain Climbers
Lateral Hops
Oblique Push Ups
Jump Squats
x2