The Center for Ecoliteracy. They call themselves a "leader in the green schooling movement" and they are doing some of the most important work in the world right now. Their programs focus on connecting children with nature and healthy food and creating a generation invested in sustainability.
As a former elementary school teacher, I am thankful that someone is bringing this work into the classroom. Programs like the ones the Center for Ecoliteracy creates are going to be instrumental in reshaping society's views on nature.
The center recently posted an article on their blog about children at a New Orleans school that have challenged their school to become less oil dependent. Check it out. This is just the kind of thinking the center aims to instill in the children it works with.