This site is cool. Its called VectorPark. Name doesn't really explain how fun and interactive it is. I've been playing on it for over an hour. :) procrastination at its finest. And so far this is good brain stuff for me and i bet for kids, too. I haven't ran into anything questionable. It makes you think. And its challenging. I did the one called LEVERS and FEEDTHEHEAD. both quirky and fun. But i have to stop.... cause its too much fun.
Go try it.