Plastic

My Plastic-free Life (Beth Terry, an authority on going plastic-free)
The Story of Stuff Project’s The Story of Plastic
Plastic Free July (efforts can be applied year-round!)
Algalita, founded by Captain Charles Moore
Pollution

Litterati: A Litter Free World. Read my full post on Litterati!
Ocean

Zero Waste

Bea Johnson @ Zero Waste Home
Kathryn @ Going Zero Waste
Catalog Choice (to stop junk mail)
Endangered Species

Jeff Corwin has many shows, several books, and is featured in a lot of online content. Follow him on his facebook page to see his newest adventures and missions. I reviewed one of his books and you can read it here.
Joel Sartore, National Geographic and creator of the Photo Ark. Read my article about Joel Sartore!
The Whale Sanctuary Project is working to establish a model seaside sanctuary where captive cetaceans (whales and dolphins) can be rehabilitated and live in their natural habitat. Read my article about them too!
Toxic Ingredients

The Environmental Working Group
Asbestos causes cancer and is in many of our homes and in the products we buy. Asbestos.com by The Mesothelioma Center is a for-profit site that provides many free articles and guides related to asbestos: Asbestos Products, Asbestos in Moldable Plastic Products, Asbestos in Home Goods and Toys, a Guide to Asbestos in the Home, and a Guide to Handling, Disposing and Recycling Asbestos.
Education

GreenEcoWarriors.org: Their mission is “Creating a Culture of Sustainable thinkers” through education aligned with national standards. I learned about this organization from reading Pesky Plastic: An Environmental Story by the founder and CEO of GreenEcoWarriors.