This year, many businesses are participating, too. IKEA will celebrate all day by turning off unnecessary lights and sponsoring climate-related competitions among customers and workers. Harrah's is turning off external lighting on all of its casinos (the Vegas strip will be dark!), and Coca Cola is cutting power to brightly lit signs around the world, including the famous sign in NYC's Times Square.
The main aim of the project is to raise awareness and mobilize a large amount of people for the cause. It's amazing how loudly shutting off the lights can speak when millions of people take part. "Earth Hour" has been a trending topic on Twitter since yesterday, so if you plan to participate don't forget to tag your tweets with #earthhour.