||You're in luck--there are many great step videos in this category.
If you like interesting choreography, try Kari Anderson's step videos, especially Body Tech,
Two the Max (a combination workout), and her
Great Moves Step series. Most of the CIA (Creative Instructors Aerobics) step sections are also intermediate/advanced level, and so are the step tapes by G-Force.
If you like relatively basic choreography, try
Step Reebok: the Power Workout, Charlene Prickett's step workouts, or Candice Copeland's
Gin Miller's Intense Moves has basic choreography but is a real cardiovascular challenge. This excellent interval workout may very well bump your fitness level up a notch.