National Geographic for Kids takes you all around the world! http://kids.nationalgeographic.com/
A great link to learn more about the White House http://www.whitehouse.gov/kids/
Fedstats Kid's Page - A great site that has all the links to government agencies' pages for kids. http://www.fedstats.gov/kids/index.html
Fun Social Studies - This page has interesting lessons on almost every topic imaginable! http://www.funsocialstudies.learninghaven.com/