20 minute workout...

So today I went to the Y to ask about their college memberships.
I was all ready to go and workout but unfortunately the Y was closing in 30 minutes... And it took me 10 minutes to get ready.
In other words, I had 20 minutes to workout.

Not everyone has 2-3 hours to workout per day. I wish I did, but for most of us 1 hour of working out (which also means extra time to go to the gym, take a shower, etc.) Might be hard to fit in a busy schedule.

Here is what I did today, it is more of a cardio workout but also has strength exercises:

10 minutes on the treadmill. Incline at 2.5 and speed from 5.5 to 6 (fast enough to make me sweat.)

2-3 rounds of 3.5 minutes each of squats, ski hops (or whatever kind of jumping that was), crunches and push ups (from the training assistant/cross fit app I wrote about in my earlier app.)
Push ups were awful. I have no arm strength whatsoever.

So anyway, doing all of these equals to a 20 minute pretty intense workout.

What do you like to do when you only have 20 minutes to workout?