This fusion practice from Kate Kendall is a moderate class designed to quickly build your power with a little body-weight strength training.
This hatha practice from Jo Schaalman is a moderate class designed to build your center and invigorate your experience.
Planks, bridges and butterfly sit-ups are the "core" of Ashley Borden's third workout. It is designed to strengthen your midsection, trim your waist and kill more calories.
This vinyasa practice from Nico Luce is an intermediate class designed to strengthen the spinal stack and release that upon which it sits.