What are major sites doing to draw attention to Earth Day this year? Glad you asked...

Google continues the tradition of replacing its logo with new artwork on special days, which links to a simple Earth Day search this time around. The company has also been making strides to lower its environmental impact.

Yahoo is also having fun with its logo, opting for a neat little animation instead. They also launched a microsite and have announced that they are going 100 percent carbon neutral.

MSN leads with a Places in Peril photo gallery, an article on the plug-in car, tips on going green the easy way and a Stop Global Warming microsite.

Digg doesn't appear to be commemorate the day in any special way, but its users are keeping its Environment category humming.

Update: EcoGeek has an interesting interpretation of how the Google Earth Day logos have evolved during the past six years.