I know, Earth Day is not until April 22, 2007 - but as an educator, we tend to plan ahead. Actually, I was reading my feedblitz today and there was an entry from the Sun Link Blog about a virtual ribbon. Planetfesto is creating a virtual ribbon to honor Earth Day. It's pretty simple - you find your favorite "earthy" picture (they have a few that you can choose from or you can upload your own). Next you write why you love the planet, what you personally do to protect it, and click on additional things you plan to do to help keep your planet green. There is even a link to lessons for grades 1-6, but I bet this is something High School kids would be interested in too. There's one link of the ribbon from an 80 year old woman.
Looking for more ideas for Earth Day? Check out Instructor Magazine, Parent and Child, or this list of Earth Day web sites.