Math Open Reference is a great site that contains lessons on a wide variety of topics. This site includes numerous interactive animations that students can control and manipulate as they learn the concepts.

Great site that contains indepth lessons on a variety of topics. This site uses numerous applications and real - world references to help illustrate concepts.

This website is a little more complicated than desmos, but it is an unbelievably powerful tool that can be used to solve problems in any course including geometry and calculus. Pretty useful for physics as well. The program can be opened as a webpage or downloaded to your computer for offline use. Geogebra is also a very easy way to make geometric drawings and charts that can used for projects in all of your classes.

This website has an awesome graphing calculator that you can use for a variety of problems.

Visit Khan Academy to find online lessons on countless topics.