(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/
American Library Association Great Web sites for Kids http://www.ala.org/gwstemplate.cfm?section=greatwebsites&template=/cfapps/gws/search.cfm - 16k - Cached
Dutchess BOCES iCampus http://galileo.dcboces.org/icampus/