From Boing Boing I came across this article by Mark Frauenfelder on Having Fun with Your Finances in Credit.com (April 25, 2011). The article reviews two sites that gamify your home finance goals, payoff.com and smartypig.com. It sounds like smartypig is the best, but is also still in beta.
I suspect we are going to see an explosion of sites gamifying things (and I’m actually working on one too.)