White House for Kids http://www.whitehouse.gov/kids/whlife/index.html
National Geographic for Kids http://www.nationalgeographic.com/kids/
Fun activities - by girls....for girls. http://bensguide.gpo.gov/3-5/index.html
Math for kids, multiplication review, flash cards, etc. http://www.coolmath4kids.com/
http://www.funbrain.com
Internet 4 Classrooms 4th grade skills. There are several math practice games, including flash cards. http://www.internet4classrooms.com/skills_4th_original.htm
Read, write and think is a great Language Arts site. http://www.readwritethink.org
http://www.scholastic.com