http://www.quia.com/dir/math/
Games and quizzes for learning academic concepts. Great review ideas for all grade level and skill levels.
http://www.aplusmath.com/
This web site was developed to help students improve their math skills.
http://www.starfall.com/ - Great reading and phonics site.
http://www.funbrain.com/ - Great games and quizzes for review of math skills.
http://www.learninggamesforkids.com/
http://sheppardsoftware.com/ (big variety of interest)
http://www.aaamath.com/ - Interactive practice and basic skills by grade level. Really neat!
http://www.multiplication.com - Great site for reviewing multiplication facts.
http://www.eduplace.com/edugames.html - Brain Teasers provide weekly math challenges for students in grades 3 and above.
http://www.itsawordfunworld.com/ - Great Language Arts skill builder.
www.ixl.com
www.mathcats.com/ - Practice math facts online.
http://www.funattic.com/game_card.htm
www.harcourtschool.com (all subjects including science!)
www.nancydrew.com
www.enchantedlearning.com
http://www.hoodamath.com/
www.superkids.com (math quizzes, logic, vocabulary and more.)
Just for Fun!
http://www.scholastic.com/kids/
www.gamekids.com
www.americangirl.com
www.nick.com
www.pbs.org/kids