A Book In Time - History book lists with reviews, crafts, activities, games, maps, timelines and more.
Baldwin Project - Lots of ebooks in the "history" section.
Beacon Learning Center - A few social studies lessons on various topics.
Classics for Kids - Learn about musical composers.
American Heritage - History curriculum for elementary, middle school, high school, or teachers.
America's Story - Elementary level. Learn about famous Americans, states, hobbies, etc.
Ben's Guide - US government for all ages.
Bill of Rights Institute - Learn about the US Constitution.
Civil War Trust - Learn all about the American Civil War.
Congress for Kids - Learn about American Government.
Digital History - Lots of American History by era.