And the winner is...

MIT Open Courseware
This is a truly amazing site. In the words of the winning contributor, Marc Pou, "Here you can find high quality free courses to boost your knowledge in different areas from one of the most recognized universities in the world."

I agree with this description. From literature to management and beyond, entire university and graduate level courses are offered here, with complete documentation, all without any cost or subscription requirement. For me, this is a great example of an organization using the internet to full potential.

Congratulations, Marc! And thank you for this great addition to the links list of Thinking in English!