What English learning websites or channels are best?

It never made sense to me that every teacher should re-invent the wheel to feed the desire for ‘content’ when there is already excellent material around the web.

Here are some of my favorites for English learning at higher levels.

Sentence-level writing resources:
https://owl.purdue.edu/owl_exercises/index.html

Text-level writing resources:
https://owl.purdue.edu/owl/purdue_owl.html

YOUTUBE TEACHERS
Jennifer ESL and ENGVID are popular youtube channels on tenses, concepts, structures that are worth mastering.  Jennifer ESL teaches clear lessons on all aspects of grammar, whereas ENGVID is a consortium of teachers who provide entertaining ‘chalk and talk’ lectures on all aspects of English language learning (test-taking, grammar, reading, pronunciation) Rachel’s English is excellent for pronunciation and connected speech.