iCivics.org is a great resource for secondary educators teaching social studies, government, and civics courses. Originally founded by former Supreme Court Justice Sandra Day O’Connor, the non-profit site provides full-unit lesson plans, interactive activities and games to engage students on important topics such as the foundations of government, the Constitution of the United States of America, and the 3 branches of government. There are also a wide variety of interesting games to help students apply their knowledge in real-life situations. (The games are created in part by Filament Games – the same company who works with the JASON project and BrainPop!)
All of the materials on the site are free, but there are additional resources and game-play options when teachers and students create free accounts. I forwarded the link to the Social Studies teachers on my campus, especially since a lot of the curriculum matches up with the 8th Grade curriculum here in the state of Texas. It seems like they have enjoyed using it so far – hopefully it can help you, too!