It's Earth Day, do something nice for your planet :-D
Now granted, everyone, everywhere should try and do something nice for their planet every day of the year (it being the only one we have and all), but at the very least on this day try to keep it on the forefront on your minds. Cool?
Cool.
So, to kick off, we have the Earth Day Network; which provides lots of good information about the happenings surrounding this Earth Day (and next year's big 40th anniversary Earth Day extravaganza). They also have lots of links to Earth Day events and happenings round and about the US, Canada, Australia, the UK, and several other European countries. Lots of info there to be sure.
Next up, we have the ever useful and popular Treehugger and their Earth Day page. There is an insane amount of content at that site folks. With links to just about anything environmentally-related that you can imagine. Need a green buying guide? They have that. How about info on sustainable design and architecture? They have that too. Be sure to check out the links on the sidebar as well, as they are just full of useful sites.
Then there is Global Stewards, which provides a whole slew of "environmental tips and sustainable solutions for a healthy planet." Highly informative and useful.