Xtra Math https://xtramath.org/#/home/index This is the place to practice math skills.
National Council for Teachers of Mathematics Brainteasers http://illuminations.nctm.org/BrainTeasers.aspx?id=5030 Great brainteasers that have PDF downloads for the question and the answer.
NRich http://nrich.maths.org/frontpage This website is out of Cambridge, England, and has games divided out for students in upper primary and lower primary.
United States Mint http://www.usmint.gov/kids/ 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.