Research shows that fluency with basic math facts is developed through a strong understanding of the four operations and an emphasis on conceptual strategies for retrieving those facts. Below are some online resources to support your child as they progress through the Math Wizard Levels. 
Resources for Kindergarten to 2nd Grade
Resources for 3rd Grade to 5th Grade
Apps
ABCya.com 

My Math Flash Cards 
Sushi Monster 

Math Puppy 
Rocket Math 

Tic Tac Math Universal 
Hungry Fish 
Fast Facts 