I find that using technology as an aid to help students visualize abstract mathematical concepts improves student success.
Desmos has a graphing calculator, activities covering most standards, and allows educators to create their own activities. Click the image to learn more about Desmos.
Geogebra (Geometry and Algebra) is a powerful web app that allows for geometric transformations, algebraic function graphing, fraction visualization, 3D graphing and illustrating, and also user-created resources. Click the image to learn more about Geogebra.
The TI-83 virtual calculator application is extremely useful for showing students calculations on a realistic calculator using an interactive smartboard or projector screen. The TI-83 is a dated calculator, but shares many of the same functions and button layout of newer versions. Click the image for instructions on downloading the application.