PBS Kids http://www.pbskids.org.
Fun Brain http://www.funbrain.com
Surfing the Net with Kids http://www.surfnetkids.com
National Geographic for Kids http://www.nationalgeographic.com/kids/
Seussville http://www.seussville.com
Ask Jeeves for Kids http://www.ajkids.com
Enchanted Learning http://www.enchantedlearning.com
Scholastic http://www.scholastic.com
Discovery Kids http://www.discoverykids.com
Time for Kids http://www.timeforkids.com