National Library of Virtual Manipulatives

Here's a site with a huge amount of math manipulatives with your students.  Everything from base ten blocks, to virtual calculators, to pie charts... there are really too many to many to talk about.  Everything is categorized by grade and by program (algebra, geometry, number and operations, and more).  This is a great site for math.  Really great for use with an interactive whiteboard like the smartboard!

Website:

http://nlvm.usu.edu/en/nav/vlibrary.html