Great Science Fun (Gr. 2-5) http://tryscience.org
Super science site by the National Academies. Girls will especially like it. http://www.iwaswondering.org/
Have fun aboard the Magic School Bus. http://www.scholastic.com/magicschoolbus/home_2.htm
Explore science in Wonderville 3D. http://www.wonderville.ca/
Grades 3 through 5 loves Bill Nye the Science Guy. http://www.billnye.com/
If you love SPACE, you'll love this site! http://edspace.nasa.gov/home.html
Unleash the Beast... Science Monster! http://www.sciencemonster.com/
If you like space and rockets, you MUST check out this website. It's brought to you by NASA. http://www.nasa.gov/audience/forkids/kidsclub/flash/index.html
Science to the EXTREME! http://www.extremescience.com/index.html
Interested in bats?????? http://www.bats4kids.org/
Space and other fun things! http://kids.f9.net.uk/flash/planets/about_planets.html
Awesome website. All sorts of science topics. Yes, there's games too. http://sciencenewsforkids.com/