This is a full body workout which uses only your body weight (no equipment at all, not even bands) and I first came across it when it was being used as a warm up at the start of Krav Maga sessions. It's an excellent combination of resistance training and cardio (thank you burpees).
20 pushups
20 sit ups
20 squats (full range of motion, ass to the grass)
20 burpees
20 jumping jacks
Repeat this entire circuit 3 times with minimal rest in between circuits. This makes for 300 movements altogether and that's why it's called the 300s.
Better yet, repeat the entire circuit as many times as you can. 4 times, 5 times, 6 times etc. and rename it.
