This site, provided by Edhelper, offers many great free activities and projects all geared towards a better understanding of social studies topics, including: Canadian Theme Unit (units for individual province, books, leveled reading comprehension activities, maps and biographies), Country Theme Units, Economics, Famous Educators, Geography, History of Mathematics, How Can I Help?, Explorers, Biographies, Crime and Terrorism, Ancient America, Ancient China, Ancient Egypt, Ancient Greece, Ancient India, Ancient Mesopotamia, Ancient Rome, World Religion, Middle Ages, Renaissance, European History: 1600s-1800s, Inventors and Inventions, World War I, World War II, History of Books and Writing, World Wonders.
There are also sections on Document Based Activities, World Problems and Issues, Social Studies Mixed Review Practice (Grades 1-6), Life Skills, and Time Lines.