Earth Day turns 40 today. But before you plant a tree, swap out an incandescent bulb or run out and buy the Avatar DVD (or Avatar Blu-ray), which was released to coincide with Earth Day, I suggest that you watch this excellent Earth Day episode of American Experience on PBS. Sure helps put things in perspective, and it’s riveting to boot.

To see how IT heavy hitters are marking the occasion, just visit their websites. You can always count on Google to rock a fun new logo. Microsoft makes the case for employing software to improve the world. This year, the focus is on Hohm, cloud-based environmental monitoring and the Bing Earth Day photo contest. Apple’s currently a little iPad obsessed, but there’s good info to be found in the environmental section of its site.

If you happen unearth a good link, share it in the comments!

*This post will be updated throughout the day.

Update: Check out NASA.gov for amazing, desktop wallpaper worthy photos of Earth like this one:

Read: Earth Day at 40: What Good Is It Now? – National Geographic

Now, 40 years later, Earth Day is every day, as the saying goes. The thing is, it’s also everyday–environmentalism has become a routine, if not universally embraced, part of U.S. culture, with green-ness as much a marketing tactic as a moral pursuit.