I have both of my kids, 16 & 19, utilizing the Khan Academy website. I learned of it last year while watching one of Stossel’s education shows about charter schools, etc.
It is GREAT. With over 4,000 videos. I mentioned it to my daughter who was away her freshman year and majoring in Chemical Engineering . . . some of the professors have a very difficult to understand accent combined with a difficult subject, AP Chemisty or whatever her Calculus or Physic level classes were, and even at college level, up through maybe sophomore classes, she found the videos very helpful to watch after certain lectures on chapters or sections and prior to exams for review.
Now, I’m trying to get son, junior in high school, to utilize the videos to up his ACT score. Plus he is taking three AP classes this year.
I plan on sending a small donation . . . of course nothing quite so significant as Bill & Melinda Gates, but the videos are a great resource. I even tell other parents, the kid who carries my groceries out at the store who mentions he is taking Organic Chemistry in high school, just about anybody who I think they might benefit . . .and they quickly add the name/website into their cell phone. :)
Khan Academy is great. Wonderful courses!
Also.....For anyone who is serious about math I recommend the Saxon Math books. Always get the solutions book as well.