Excellent mechanics, grammar, usage, spelling (MUGS) site that allows you to work at your own pace and customize some of the content of the examples with sports, celebrities, music, etc.
Great place to work at your own PACE!
Customized news feed that is more visual than text.
I cannot stand RSS feeds -- this, however, makes me crave more news. Similar to Flipboard, but less ornery on my classic Android Incredible v1.0
TED is chock full of amazing content from the world of thinking, making, creating, innovating, etc.
Most folks know about it by now, so why include it? TED-Ed for one, but for two, it is transformative for enabling customized delivery of the content with piles of UDL features. It's just awesome.