Mathematica has defined the state of the art in technical computing and provided the principal computation environment for millions of innovators, educators, students, and others around the world.
This website provides instructional videos and practices for any grade level. It gives students step by step video explanations and practice problems on the topics chosen. The topics range from simple to complex problems of not only math but other subjects as well. 
Desmos is a website used to graph functions, plot data, evaluate equations and more. This is a website used often by math professors to project sample problems and give students a visual representation of examples.