http://earthobservatory.nasa.gov/
http://www.nasa.gov/topics/earth/index.html
Visit the National Aeronautics and Space Administration's Earth Day Posters page.
Visit the National Aeronautics and Space Administration's eBook page, which includes the below book, Earth.
Be sure to checkout NASA's Earth as Art free eBook!
page 5, Aleutian Clouds, Bering Sea