"Mr. Robb's Math is a YouTube channel containing 555 videos produced by high school mathematics teacher Bradley Robb. Mr. Robb's videos explain and demonstrate solving problems in Algebra I, Algebra II, and Calculus. Most of the videos are recorded while Mr. Robb is teaching. You can find the videos on the Mr. Robb's Math YouTube channel or visit Mr. Robb's website WowMath to find the videos organized in sequence with accompanying screenshots."
Check out the activities on this site, which give students immediate feedback. I looked at the math activities for Algebra/Geometry. Students can test their understanding of concepts quickly using this platform. Check it out!