Learning can be fun...
www.ixl.com
http://www.funbrain.com/
http://www.mathgametime.com/
http://pbskids.org/
http://juniebjones.com/
http://pbskids.org/arthur/
http://kids.nationalgeographic.com/kids/
www.abcya.com
http://www.math-drills.com/addition.shtml#BLM
http://www.coolmath.com