I second the recommendation for Billy Blanks DVDs.
I have the following:
Ab Boot Camp
Basic Training Boot Camp
Ultimate Boot Camp
Fat Blasting Cardio
Tae Bo Cardio Circuit 1 & 2
Cardio Boot Camp Live
and can honestly say they kick my butt (even without the resistance bands!) and I consider myself between an intermediate and advanced fitness level.
I always have a blast doing the workouts, Billy has great energy to keep you motivated, and Shelley is an inspiration. A good way to get a mix of cardio and strength training in one hit, which I find helpful on the days I find myself unable to run outdoors (usually due to bad weather).
I am really excited to try them WITH the Billy Bands (which I have just got).
Check out YouTube to get samples of the videos so you can get a good idea of what you're in for!
Physical fitness can neither be achieved by wishful thinking nor outright purchase. – Joseph Pilates