(Sample link) NASA for middle-school students http://www.nasa.gov/audience/forstudents/5-8/features/index.html
(Sample link) National Geographic for Kids http://www.nationalgeographic.com/kids/
CIA World Factbook http://www.odci.gov/cia/publications/factbook/geos/rs.html
Ancient China to Modern Times http://members.aol.com/TeacherNet/AncientChina.html#Ghengis
Good Student site http://bensguide.gpo.gov/6-8/index.html