(Sample link) National Geographic for Kids http://www.nationalgeographic.com
http://www.starfall.com
http://www.funbrain.com
http://www.playkidsgames.com
http://www.scholastic.com
http://www.pbskids.org
http://www.sciencenewsforkids.org
http://www.primarygames.com
http://www.wxdude.com
http://www.kidsastronomy.com
http://www.nationalgeographic.com
http://www.whitehouse.gov