This is a great website for kids to learn about our government. It contains theme units (grade level specific) students can access. In each unit are interactive games and slide shows students can view to learn more about our nation/government. My students love to visit this site.
National Center for Education Statistics Dare to Compare allows students to check what they know about subjects (social studies, math, science) compared with other US and international students from a 600+ question database. The "Create A Graph" page is a useful interactive tool for teaching ways to communicate statistics.