Here are 11 dynamite sites where you can "go eco" and find environmentally-oriented lesson plans:
Lesson Plans from EarthDay.org
Read-Write-Think: Reading and Writing About Pollution to Understand Cause and Effect
Global Environmental Issues: What Are the Worst 9 Environmental Issues Globally?
Discovery Education: Protecting our Planet
EekoWorld @ PBS Kids
Learning to Give, Earth Connections (A site dedicated to philanthropy education)
Science Lots of Lessons
BrainPop Educators: Water Pollution Lesson Plans
Teach Engineering: What's Air Got to Do With It?
Image from https://www.shbarcelona.com/blog/en/tourism-internship-with-go-eco/