• Children and Nature Network
• National Environmental Education Foundation
• PBS's The National Parks: America’s Best Idea, by Ken Burns - Educator’s Resources
• Sierra Club's Building Bridges to the Outdoors
• Texas Master Naturalists
• Texas Parks & Wildlife Magazine - "Keep Texas Wild" Teacher Resources

Recommended Reading
Last Child in the Woods: Saving Our Children from Nature-Deficit Disorder
by Richard Louv

These grants are available for teacher applications.

• DonorsChoose.org 
• Impossible Possibilities
• Lowes Toolbox for Education
• Sonic's LimeadesforLearning.org
• Target Field Trips: Take Education on the Road
• Wild Ones