I just came across an article, in the Web Site Social Media Examiner. This could come in handy, when you have to write something.
I will mention them:
Write Rack https://writerack.com/
Slick Write https://www.slickwrite.com/#!home
Polish My Writing https://help.plagtracker.com/
Essay Mama http://writefullapp.com/
Grammar Monster http://www.grammar-monster.com/
Papers Gear http://www.papersgear.com/editing/
Hemingway App http://www.hemingwayapp.com/
Hope you use them! Share Web Sites that maybe you know of.