Here's a high intensity cardio that you can do on your own.
I just read about this workout from Bruce Lee's The Art of Expressing the Human Body. And if you are wondering, yes that is what I do with my time all day. I love reading about training and human possibility.
According to the book this workout was one of Lee's favorite interval training programs.
Here's the workout:
-jog x 60 seconds
-run (sprint) x 30 seconds
-walk x 60 seconds
Build up to 10-20 rounds, and you've got an incredible workout. I'm definitely going to give this one a try myself.