When I was having a browse through some of the many cool Gogofrog sites that people have made, I stumbled onto this interesting, thought-provoking site called Cool Science Projects.
Cool Science Projects point you to some exciting projects you can undertake to get you thinking and get your hands dirty! They range from really easy-to-do ones like manipulating the colour of a rose, to some more advanced ones like mathematically driven pulley and lever systems. It's also explained why the results are so - food for the brain! Be sure to check it out!