Here are a few mathematics links you may find helpful:
Khan Academy - Videos on everything from Arithmetic to Calculus. - Games, videos, tricks for learning times tables.
Print Free Graph Paper - Print graph paper at home.  Helpful for math homework.
IXL - Online Math Practice.
Xtramath - Free online practice to increase addition, subtraction, multiplication, and division skills/speed.
Multiplication Baseball Game - A third grade Everyday Math game.
Hooda Math Games - Online Math Games.  - Free Math Games.
Math Warehouse  - High School Level Math resources.  Algebra, Geometry, and Trigonometry.
Math and Business Games for Kids - A collection of online and printable math and business games.