American Chemical Society
American Chemical Society: Explore Chemistry: Water and Chemistry
Explore water's unique properties in the activities here. Includes ideas for starting a chemistry club, ideas for Earth Day, articles, and videos.
Smithsonian Institution
Smithsonian Environmental Research Center: Forces of Change:meet Your Atmosphere
This superb site has detailed information about the composition of the atmosphere, how it is always changing, how it protects life on earth, and the destructive impact human activity has on it. There is an atmosphere design lab, as well...
Other
The Greenhouse Effect: Natural and Amplified Warming
This concise resource presents a thorough drawing which simplifies the explanation of the greenhouse effect into six easy to understand steps.