Interactive Math Fun
with online manipulatives (organized by grade levels and math strands ) from the National Library of Virtual Interactive Math Manipulatives
(you will need a laptop for the graphics to work on this site)
http://matti.usu.edu/nlvm/nav/vlibrary.html

Interactive Math Virtual Manipulatives
http://matti.usu.edu/nlvm/nav/grade_g-2.html