General Reference

ALA's Great Sites for Kids - http://www.ala.org/greatsites

Dictionaries

Merriam-Webster Online - http://www.m-w.com/

Math Dictionary - http://www.amathsdictionaryforkids.com/

Foreign Language Dictionary - www.wordreference.com

Encyclopedias

Grolier Online - www.go.grolier.com

Science and Mathematics Encyclopedia - http://scienceworld.wolfram.com/

Facts

Fact Monster - www.factmonster.com

World Almanac for Kids - http://www.worldalmanacforkids.com/

Maps

Atlapedia Online - www.atlapedia.com

Biographies

Biography - www.biography.com

Infoplease - http://www.infoplease.com/people.html

Presidential Biographies - http://www.whitehouse.gov/kids/presidents/

Special Areas

Science- http://www.science.gov

CIA Factbook- https://www.cia.gov/library/publications/the-world-factbook/index.html