A very robust online classroom that includes discussion, quizzes, calendars, polls, gradebooks, assignment annotation, and much more. Very dynamic and free.
The help centre provides video tutorials: http://help.edmodo.com/?subdomain=www
The Khan Academy is a non-profit educational website created in 2006 by educator Salman Khan, a graduate of MIT and Harvard Business School. The stated mission is "providing a high quality education for anyone, anywhere".
The website supplies a free online collection of more than 4,000 micro lectures via video tutorials stored on YouTube teaching mathematics, history, healthcare, medicine, finance, physics, chemistry, biology, astronomy, economics, cosmology, organic chemistry, American civics, art history, macroeconomics, microeconomics, and computer science. Khan Academy has delivered over 240 million lessons.