Entertainment Resources:

Internet Movie Database
The Leaky Cauldron
Backstage West
Hollywood Reporter
PBS
A&E
BBC
YouTube

Mathematics:

Roman Numerals 
Math Forum 
Math Page
MIT World Web Math
Algebra
Calculus on the Web
Math Reference Tables
Planet Math

Internet Resources:

Webopedia
Google
Excite.com
Northern Light
IT Encyclopedia

General Information:

Wikipedia
Library of Congress
The World Factbook
Photo Vault
MIT Open Courseware
How Stuff Works

Social Science

World Embassies
Nolo(US law)
U.S. Senate
U.S. Congress

Travel:

Time Zones
Currency Converter
Mapquest

Medicine and Health:

EMedicine
Mayo Clinic  
Web MD
Myozen
Virtual Hospital


Science:

Science made Simple
Scientific American
"Ask the Experts"
Periodic Table
Physics
"Optics and Microscopics"
Astronomy Cafe

Language Arts:

Merriam-Webster Dictionary
Cambridge Dictionary
World Wide Words
Wordsmith.org (word of the day)
Double Tongued Dictionary
Urban Dictionary
British Terms
Babel Translations
Elvish
Acronym Search
Lingolex

News Media and Information:

New York Times
The Boston Globe
The Washington Times
Detroit Times
Snopes (urban legends dispelled)
Chronicle of Higher Education
CNN
NPR

Books and Literature:

Bartleby.com (literature, verse)
Questia (on-line library--free previews)
Book Crossing

Social Reform:

ACLU
Amnesty International
MLK Papers
Greenpeace
Oxfam America
National Organization for Women

Directories:

Web Radio Directory
White Pages