Xtra Math
This is the place to practice math skills.

National Council for Teachers of Mathematics Brainteasers
Great brainteasers that have PDF downloads for the question and the answer.

NRich    
This website is out of Cambridge, England, and has games divided out for students in upper primary and lower primary.

United States Mint      
Are you interested in the history of money?  Would you like to know where our money comes from when it’s brand new?  Visit the United States Mint.  Check out the Games, Cartoons, and Time Machine of Coin Mysteries.