Holt McDougal Online-We use this website for Algebra in which there is an online textbook so students don't need to take their 10 lb book home. But what I LOVE about this site is that there are short videos which explain and show you how to do math problems. It's like having a video tutor at home! Also, there are interactive problems, self-quizzes, and games too! Talk to your math teacher to find out if your math book is available online and instructions to how to register or click here.
Math is Fun-BEFORE YOU CLICK ON THE LINK, READ THIS: I am aware the website looks like it's designed for elementary school kids. But if you're taking statistics or calculus, they have some GREAT, easy to understand lessons. In fact, if you're taking ANY math and are looking for some help. They have everything from working with the metric system to integrating to figuring out standard deviation to tessellations. What's unique about the lessons is they are made to be simple and easy to understand.
Plotly-Plotly is a neat way to be able to visualize data. Remember using bar graphs and pie charts? Yeah those are just fine...NO! Not anymore! Plotly offers a ton of different types of charts, graphs, and images to visualize your data! Not only that, but Plotly can also analyze your data (standard deviation and outliers) and do simple computations (like finding a line of best fit).
Khan Academy-Of course I was going to mention Khan Academy! Khan Academy has a huge collection of easy to understand videos for nearly every subject matter. The videos are categorized by subject and topic so it's also really easy to navigate. Though the videos may not be visually exciting or anything, the content is superb! I use them all the time for algebra but wouldn't hesitate to use the videos for statistics, economics, and science