Lots (1600 and growing) of short videos, low-tech so they load easily even on low-grade home computers. Each video is like a very charming talking blackboard - you hear, you see, you understand. Low-tech, low stress.
All of them created by one man, Salman Khan, who describes his work like this:
I teach the way that I wish I was taught. The lectures are coming from me, an actual human being who is fascinated by the world around him. The concepts are conveyed as they are understood by me, not as they are written in a textbook developed by an educational bureaucracy. Viewers know that it is the labor of love of one somewhat quirky and determined man who has a passion for learning and teaching.
I don't usually like online learning packages much but here it's not the technology you take note of, it's the way it all makes sense.
And what an end: "With just a computer and a pen-tablet-mouse, one can educate the world!" Inspirational.