I have started doing power circuits to get my cardio up. I have been running a mile for time as a warm up, and then proceed with a couple of core/stability exercises, and then 4 sets of a heavy strength/power movement. I then follow that up with a giant set of 3-4 exercises, selected from core multi-joint movements. The rep ranges are submaximal 6-8 on most of the giant set movements. This has gone very well for me thus far, except in the busy gyms it can be hard to do circuits. Here is what my first workout doing this looked like:

Warm-up 1 mile run

4x20 sets overhead squat (light)

4x20 sets snatch balance (light)

4x3 mid-hang power snatch(heavy)

4 sets of the following, performed in circuit:

clean and jerk; chin up(weighted), push up(to failure), situps (to failure)