Khan Academy is a "free online collection of more than 4,300 [...] YouTube video tutorials teaching mathematics, history, healthcare, medicine, finance, physics, chemistry, biology, astronomy, economics, cosmology, organic chemistry, American civics, art history, macroeconomics, microeconomics, and computer science." (Wikipedia)
Crash Course is an educational YouTube channel by the "VlogBrothers" with a series of video tutorials on World History, US History, English literature, Biology, Chemistry, and Ecology.
The Encyclopedia of Life is a free, online encyclopedia of the 1.9 million species known to science. (Wikipedia)
HowStuff Works explains thousands of topics, from engines to lock-picking to ESP, with video and illustrations so you can learn how everything works." (HowStuffWorks.com)