The internet is a wonderful tool for families.
Here are some of my family's favorites:

The Parent's Guide to the Information Super Highway
Safe-Kids on the Internet - Internet Safety Tips
Boston's Children's Museum
National Geographic for Kids
Kids Space
Electronic Zoo - by NetVet Veterinary Resources
The Encyclopedia Mythica - An Encyclopedia on Mythology, Folklore, and Legends
The Magic School Bus
BJ Pinchbeck's Homework Helper
Yahooligans - the Web Guide for Kids
Crayola Crayons - The power of creativity
CIVITAS - An international, non-governmental organization dedicated to promoting civic
  education and civil society
• US Congress - THOMAS - Legislative Information on the Internet
• World population - Click here to see the world population
Travelocity - Great site for planning and budgeting family vacations - Cool advice on bugs, worms, and other gross stuff