University of Saskatchewan (Canada)
Emr: Exercises in Math Readiness
Practice your mental math skills with this site, where practice problems in addition, subtraction, multiplication, and division abound. Introductory, intermediate, and advanced levels are available. Just type in your answer and you'll...
Other
Curious math.com: Math Is an Attitude
This site offers numbers tricks to help multiply and divide large numbers mentally. There are also tricks for powers and roots of numbers.
University of Cambridge
University of Cambridge: Nrich: Make 37
Sharpen your logic and addition skills while working on this challenge. Solution.
University of Cambridge
University of Cambridge: Nrich: Magic Squares
In a Magic Square all the rows, columns and diagonals add to the same number. This number is called the Magic Constant. Learn math fundamentals visually and have fun at the same time.