The U.S. EPA's Climate Change Kids Site offers comprehensive information on the issue of climate change in a way that is accessible and meaningful to kids. Its nine sections detail various aspects of climate change:
Lesson Plans for Educators
EPA has compiled seven lesson plans on climate change developed specifically for middle school students. The lesson plans and related classroom activities are tailored to meet the National Science Learning Standards, and the majority can be completed in one class period of 45 to 60 minutes. Topics covered by the lesson plans include: the difference between weather and climate, the sources of greenhouse gas emissions, the carbon cycle, sea level rise, and the impact of climate change on coral reefs. The lesson plans can be found on EPA's climate change website for students at http://epa.gov/climatechange/kids/resources/lesson-plans.html
The site also has a climate change calculator, games, links, stuff for teachers and more!