Yes, save the earth while you sleep! Okay, so not really save it! But help!
I thought of a not so commonly thought of way of "going green" last night. Get more hours of sleep! Yes, it is WONDERFUL for your body, but it also keeps you from having the lights on. Think about it, if you usually stay up until midnight, and instead you go to bed at 10 pm, that saves two hours of the lights being on. And not only the lights, but you wont be up to be doing other "electrical" things like cooking (late night snacks anyone?), watching TV, computing, etc. Hey, it might not be much, but every little bit counts right?! ;)
So in case your health wasn't a good enough reason, help the planet! Get more sleep!