For the last two weeks, I’ve been performing the following warmup to better prepare myself for our initial classes.  If I am not able to participate in the class, this drill comes in really handy, and it does not take that much time.
Kip Ups
Perform as many kip ups as you can in one minute.  This should only be to those that have done these before.
Jump Rope
Jump rope for one minute as much as you can. 
Jumping Jacks
Perform this exercise for one minute.
Running in Place
Run in place for one minute.
Pogo Hop
Hop and bounce for a full minute
Cross Country Skier
Perform the cross country skier exercise for one minute
Kip ups
Perform as many kip ups as you can in one minute.
This is a great cardio workout that is quick, but intense.  To challenge yourself, perform this routine at two, three, and fives minute intervals.