NASA for middle-school students http://www.nasa.gov/audience/forstudents/5-8/features/index.html
National Geographic for Kids http://www.nationalgeographic.com/kids/
Fun activities - by girls....for girls. http://www.missoandfriends.com/
http://www.eduplace.com/kids
Math Baseball http://www.funbrain.com/math/
Play games to give rice to nations in need! http://www.freerice.com