Reference Sources:

• Discovery School
• High School Ace
• Homework Help from About.com
• Information Please
• Internet Public Library
• Merriam-Webster Online
• Refdesk.com

Art & Music:

• Artcyclopedia
• Art History Resources
• Essentials of Music 
• Instrument Encyclopedia
• Philadelphia Museum of Art
• Smithsonian Institution 

Biography Sources:

• African-Americans in Science
• Biographical Dictionary
• Biography.com
• National Inventors Hall of Fame
• Presidents of the United States

Government:

• Library of Congress
• State and Local Governments
• U.S. Census Bureau
• U.S. Government Printing Office
• U.S. House of Representatives
• U.S. Senate
• U.S. Supreme Court
• U.S.A. Government Made Easy
• The Whitehouse

History:

• American Memory - Library of Congress
• The American West
• Exploring Ancient World Cultures
• The History Channel
• The US Holocaust Memorial Museum

Language Arts:

• A+ Research and Writing
• Bartleby.com (Bartlett's Familiar Quotations)
• Complete Works of Shakespeare
• Native American Authors

Maps:

• MapQuest
• National Geographic
• Rand McNally

Mathematics Sources:

• Allmath.com
• Internet Mathematics Library
• The Math Forum @ Drexel
• Web Math

Science:

• Biology4kids
• Brainpop
• Chem4kids
• Extreme Science
• The Franklin Institute
• NASA
• Periodic Table of the Elements
• The Science Page
• Students for the Exploration and Development of Space

Social Studies:

• CIA World Factbook
• Country Facts and Information
• Social Studies for Kids