The Department of Treasury includes a wealth of money-related info --such as a savings bond calculator, information on how money is made and the truth behind income tax. The U.S. Mint offers information and games about coins.
NASA will give students a crash course in our solar system, black holes, comets and more.
Learn how to protect the environment with EPA's Explorers' Club. This site explains recycling and offers games and art projects.
If you need a historic document for a school assignment, head to Basic Readings in U.S. Democracy, You'll find important documents, including the Declaration of Independence and many Supreme Court decisions.
For a complete list of government sites for kids arranged by topic, see Kids.gov.