P90X: best upper body workouts I've seen on video. Great rotation. Effecitive core work. Effficient use of time and effective use of recovery. Incorporates functional and traditional training.
P90 Masters (all but "core cardio"): similar to some P90X workouts. Very athletic. Time-efficient and effective.
TLT's (Particularly Jen Carman and Susan Harris workouts).
Functional fitness at its best.
Gin Miller, INtense Moves. Athletic interval step work. Straightforward. Great instructor.
Mindy Mylrea's workouts: very functional. Uses medicine ball in a very fun way.
Powerstrike: I love authentic-feeling kickboxing, and their form is wonderful.
Eionn Finn's "Power Yoga for Happiness," particularly "Magically Hips." Wonderful stretch and strengthning workout. Well led. Excellent form pointers and many options shown for different levels.
Slim Series. Good for days when I just don't feel like working out. They don't seem that tough, but the cumulative effect of the continuous movement can be felt the next day. "Firm it Up," a lower body only workout, is my favorite. "Cool it off" is a good stretch, stabilizing workout.
Firm BSS IV. The Transfirmer is one piece of equipment they got right. The incline lunges and step on the incline really work the 'thutt" area. The cardio is simple, and the variety of moves is great for days when I have exercise ADD.