I totally stold this...

From KERF, but I modified it a bit for a little more challenge. Great 10-15 minute energy boost.

Circuit One
* Push-ups (as many as you can do)
* Squats (with weightsor jump squats)
* REPEAT

Circuit Two
* Bicycle Crunches (as many as you can do)
* Reverse Crunches (ditto)
* Lunges with optional bicep curl (or curl and press)
* REPEAT

Circuit Three
* Chair Tricep Dips (feet up or down)
* Wall Squat (hold as long as you can)
* REPEAT

FINISH!
* Hold a plank as long as you can (optional raises)