BBC Wildlife site
Information and games relating to animals.

Canadian Botanical Conservation Network

Learn about the plant world.

Eco Agents                                                                                                                      
Fun and games, including a quiz, brought to you by the European Environment Agency.

Environment Agency’s Fun and Games page
Information, games and interactive animations on environmental issues in the UK.

Illinois Environmental Protection Agency

Captain Earthworm, Captain Redbird and Captain Bluegill will show you how you can protect earth's air, land and water.

Monga Bay Kids' Site                                                                                Aims to help children learn about rainforests and the environment.

National Marine Mammal Association

On whales and other marine mammals.

 

Nature Challenge for Kids

Kids' section of the David Suzuki Foundation, dealing with environmental matters.

 

Skelton Grange Environment Centre
Environmental education for children and young. Though the site says it’s for children living in West Yorkshire, most of the information is applicable to everyone.

 

TIME for kids, Earth Day
News, games, quizzes and information on environmental issues.

 

Tunza

Has separate sections for young people and children on environmental issues. Part of UNEP.

 

The Union of Concerned Scientists

Play a game to learn about how consumer choices affect the environment. Requires Java.

  

United States Environmental Protection Agency

Games and fun about our environment and how to protect it.

 

Wisconsin Department of Natural Resources

Fun electronic magazine where one can learn more about the "great outdoors".

Young People's Trust for the Environment
UK charity which aims to encourage young people’s knowledge of the environment and the need for sustainability. Lots of fact sheets.