I was at a conference the other week and got interested in the 20 Second Fitness program (http://20second.com). The basic concept is to workout for 8-12 minutes each morning in 20 second hard intervals followed by 10 second rest periods.
I am on the second ‘warmup’ week and am enjoying the program. I don’t think it will ever replace my other crazy workouts, but I like the variation and the quick morning workout to get my day started. I’ll have to see how it feels after doing the program for several weeks.