At this website, http://www.mrperezonlinemathtutor.com/ you can find an extensive array of Math power point lessons for geometry, algebra, and basic math taught in high school, middle school and upper grades. These lessons simplify planning for the teacher since the power point is ready to go and have been fully tested in the classroom.
http://www.khanacademy.org/ which boasts that they have delivered over 77 million lessons. Their library has over 2,400 educational videos and is the hot topic of debate over its flipped classroom debate. You can find videos of Khan Academy all over YouTube and ranging from how electoral colleges work, heart disease, and systems of equations.