Alliance for Climate Education, ACE. Nonprofit whose mission is to educate young people on the science of climate change and empower them to take action. Since 2009, ACE has educated 2 million students and trained over 4,000 student leaders. Example project: Climate, Our Future.
International Ecolinguistics Association, IEA. Network of 800 researchers worldwide who share ideas, opinions and articles about ecolinguistics: The role of language in the life-sustaining interactions of humans, other species and the physical environment. Official journal via open access, Language & Ecology.
National Geographic: Resource Library. Geographic resources for teachers, Pre-K-12, from the National Geographic. With lesson plans, research, maps, a storehouse of 800+ available videos, and resource library units. See example: Anthropocene Resource Library.
National Ocean and Atmospheric Administration: Just for Kids. Site promoting resources for teaching children about the environment (tides, currents, space); NOAA is part of the U.S. Department of Commerce.