Once you get to math in the higher elementary and high school ranges, it can get complex and sometimes even challenging to teach and understand. Having a way to visually show and explain concepts is very helpful.
BC Math is a website for students (and teachers) in Grades 8 through 12, offering PowerPoint tutorials for a large selection of subjects that allow for easy, repeatable learning opportunities. In addition to the lessons, there are also optional assignments / worksheets for many of the topics, and even a few test quizzes. (However there are no answers provided that I’ve found.)
Subjects seem to potentially be following the outlines of a high school text book series, divided first by grade, then by challenge level (Essentials, Principals, Honours, etc.), then chapters and subjects. Each one has explanations that help provide practice and understanding.
Unfortunately, there are a few problems with some of the presentations not working – at least I was having glitches with them, but I think that the majority work well.
It is a great site for reviewing math lessons and helping to solidify comprehension.