If you are a student and have not heard of Khan Academy you are definitely missing out. Khan Academy's purpose is to teach students with a short ten minute video on any subject including  Physics, Math, Biology, Statistics, Chemistry, Khan Academy in Spanish, and many other courses.  Here is a small biography from Wikipedia on the founder:

"Salman Khan is a Bangladeshi American born and raised in New Orleans, Louisiana. His father hails from Barisal, Bangladesh.^[2][3] Khan holds three degrees from the Massachusetts Institute of Technology: a BS in mathematics, a BS in electrical engineering and computer science, and an MS in electrical engineering and computer science. He also holds an MBA from Harvard Business School. In late 2004, Khan began tutoring his cousin in mathematics using Yahoo!'s Doodle notepad. When other relatives and friends sought his tutor age, he decided it would be more practical to distribute the tutorials on YouTube. Their popularity there and the testimonials of appreciative students prompted Khan to quit his job in finance in 2009 and focus on the Academy full-time.^"

Khan Academy  has definitely helped me out in many of my courses and I know they will help you out too.