TIME.com: 50 Coolest Websites

So, I ran across TIME.com: 50 Coolest Websites the other day. There are many great sites on here that I have tried already like Jumpcut, YouTube, and Charity Navigator, but many more to explore.

I am curious… does anyone else have experience with any of these websites that Time thinks is cool? As an educator, what would you add? Perhaps we can start a list of the 50 coolest websites for writing teachers.