Wolfram Alpha has always been my go-to site for calculations, graphing, and just about anything math related! This website it a calculator- and so much more! Just type your question in the search engine and wolfram alpha will 0utput a variety of properties/solutions. I find this site extremely useful for graphing functions because it gives you a great visual and important properties. To see how this works, click the indefinite integral for the solution, or click the Try it out! button to input your own example.

The Math Forum is an excellent site for math resources- for both students and teachers! For educators, it provides forums, lesson plans, activities, and more for every level. For students, the site offers an informative Q&A service, practice problems, and tips and tricks for any grade/level.

Math Stack Exchange is a place for discussions on a variety of mathematics topic at every level. Anyone can post a question they need help with, where anyone can answer. This site has helped further my understanding in the past on several occasions. The collaboration and sincerity on the site is truly amazing.