Math:

Khan Academy
Math from Kindergarten to Advanced Calculus
https://www.khanacademy.org/

Math.com
Math practice from the basics to calculus
http://www.math.com/

Online Multiplication Flashcards
http://www.helpingwithmath.com/resources/online_flashcards/flashcard_multiplication_x02.htm

Purplemath
https://www.purplemath.com/