PBS for kids http://pbskids.org/
National Geographic for Kids http://www.nationalgeographic.com/kids/
Starfall - Games and activities to promote reading http://www.starfall.com
Kids' games and activities for math, reading, language arts, social studies http://www.eduplace.com/kids/index.html
Learning games with Clifford the Big Red Dog http://www.scholastic.com/clifford/
Math games - parent assistance needed http://www.aplusmath.com/