I don't know if others would classify these as "circuit training", but I absolutely love Tracie Long's new Functional Foundations. She does a little bit of everything in them. There is Core Cardio and Core Strength, and both are based on the concepts of functional fitness training. Core Cardio is more cardio, but has some strength elements in it as well. Core Strength is mostly strength work, but you do some cardio. Both work the core throughout the entire workouts. They use a stability ball, light to medium-heavy weights, and a light medicine ball. Core cardio uses a basic step as well.
Forgot to give you the website in case you want to look them up: