Since we covered the World Wildlife Fund's Earth Hour earlier in the week, many more companies and individuals have vowed to participate--here's the map of the U.S. cities involved so far. 84 countries are also marking the occasion, and even McDonald's will be dimming its golden arches (via the AP). "Earth Hour is on Twitter with over 7,000 followers, and here are the Earth Hour YouTube and Flickr groups. Skype headquarters and Skype employees around the globe will be turning off lights. TreeHugger points to a Montreal ad agency's "clever if aggravating" site Ideas in the Dark. Prosper Blog lists some of the interesting buildings that will be darkened. "Hopefully," writes YERTblog, "the awareness that Earth Hour brings can usher in a new era of Earth Weeks, and Earth Months, and, eventually, non-stop Earth Years." Of course, not everyone's a believer...

Grub Street in South Africa calls it Earth Hour, Schmurf Hour: "What good will switching off our lights for an hour at 8.30pm on Saturday do for Earth? Very little, except that we'll all feel virtuous for showing that we care about the environment and then go on buying food jetted across the world, consuming vast amounts of petrol by operating two-car (and three-car) families and leaving all our appliances on stand-by." Ouch. What are you doing for Earth Hour? Let us know in the comments.