Busy schedule, hard to do weekly routines. What's a good "filler" workout?


I find it hard to do a lot of weekly fitness routines on this site since things can get very busy to the point that I may not have time to do a workout in a five-day series. I am wondering if anyone come recommend some good general "back-up" workouts that are self-contained and I can use to just hard burn some calories if I find myself breaking schedule or just need to make up for lost time.