Virtual Manipulatives by McGraw Hill

Virtual Manipulatives is an outstanding interactive math site.   Virtual Manipulatives is for grade levels K-8.

You can use options such as:

Game Boards

Adding Colors

All Mixed Up

Building a Snake

Busy Beavers

etc.

Story Boards

Bags

Baseball Diamond

Beach Playground

Bedroom

etc.

Workmats

2 Columns

Algebra Mat

Bar Diagram

Blank Calendar

etc.

Manipulatives

Algebra Tiles

Attribute Blocks

Attribute Buttons

Base Ten Blocks

etc.

Check it OUT at Virtual Manipulatives!