From the Earth Hour website:
"Earth Hour 2009 is set to switch off the globe. Already 538 cities in 75 countries, which is double the number of countries that participated in 2008, are committed. With hundreds more cities expected to sign up to switch off in the coming months, Earth Hour 2009 is setting the platform for an unprecedented global mandate for action on climate change."
There is something really peaceful about stopping, stopping it all, for a full hour. Shut off the lights, computer, television, phone...