Not sure how many people heard about this. Khan's Academy is a great free online resource to brush up on science and maths, and excellent learning/revision material for children. All 1600+ videos are made by one guy and the videos themselves are around 10 minutes each. His casual and understanding-based teaching style is probably why its so popular with millions of students of all ages. I found it captivating and made me want to go back to school.
Some News Segments