Today is earth hour day. You can support it by turning off your lights between 8pm and 9pm local time to promote electicity conservation. The first earth hour in Sydney in 2007 engaged around 2.2 million people and cut the city's mains electricity consumption by upto 10%. This one will be much bigger. And meanwhile, as a show of support, you have to admire Google for doing this:
**UPDATE:** Having seen John's suggestion, Only Dead Fish is going to be changed to a black template for the day. Great idea John.