You’ve heard of DDR (Dance, Dance, Revolution), and now there is Yourself!Fitness, developed by a Portland, Oregon company and now available for the PC (plus game consoles such as XBox and PlayStation). Here is a link to the XBox site’s review of Yourself!Fitness which is an excellent overview.
After checking it out, pop on over to the Yourself!Fitness forum and check in with people using the game.
Both excellent ways to get fit in the comfort of your own home. Your kids will love these too. You might just find yourself having to fight for time to use them actually