Math-
www.everydaymathonline.com
www.Xtramath.org
http://www1.center.k12.mo.us/edtech/edm/5.htm
http://www.conversationpieceslearning.org/cafe-math-problem-of-the-week.html
http://www.conversationpieceslearning.org/pet-shop-math-problem-of-the-week.html
www.figurethis.org
www.setgame.com
www.pbskids.org/cyberchase
www.mathschallenge.net
www.aplusmath.com
www.coolmath4kids.com
District suggested site which allows you to select grade level and search for concepts and skills to target.