I LOVE to do Step Aerobics.
So, I'd have to say Gilad's Step Workout. Gin Miller also has an ass-kicking new video called "Simply Step", which is going back to the good old days of BASIC step, leg curls, leg lifts, etc, no fancy "twist your ankle trying to learn it" choreography.

I like Gilad's step video for the same reason. When I exercise I want to breathe hard and sweat, not worry about falling on my face !