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...
National Council of Teachers of Mathematics
The Math Forum: K 12 Math Problems, Puzzles, Tips & Tricks
At this site us these tips & tricks to help students become better mental mathematicians.