One of my favorite ways to train is to combine cardio with strength in a workout. I get my heart rate up as well as build and tone muscle. The boost to my metabolism helps me burn more calories after I'm long done.
You can customize this workout:
Use hand weights in your circuit, then try this on a treadmill at home or the gym. I've even set up circuit stations in my backyard and ran around the block for ten minutes, then completed the circuit.
Take this workout on the road, and stop along your running route to complete a bodyweight, no-equipment circuit.
Add rounds for a longer workout.
Challenge yourself in the cardio portion by starting with a comfortable pace and building to a faster pace by the end round.