There are many game sites out there,, here are a few that cater to kids from the age of 3 and up.

• http://www.funbrain.com
  Ages 4+

• http://www.girlgames.com
  Ages 13+

• http://www.miniclip.com
  Ages 10+
   
• http://www.makaimedia.com
  Ages 13+