If you're short on time, then High Intensity Interval Training (HIIT) is great way to get in your cardio without spending an hour on the treadmill. You do short bursts of work with rest periods mixed in. This means you work harder, but for a much, much shorter period of time.
Sounds great, right? Well, you haven't actually tried it yet. Give one (or all) of these workouts a try and see what you think. Chances are, you'll be sweating waaaay more than you do when running on the treadmill.