Editing and Revision
The online version of Element of Style, to help you understand punctuation and grammar. Every author should have this in their library.
BetterEditor.org provides many tools such as reference material like Theasaurus and Dictionary, to Style, Grammar, and Spelling guides. You can also find translators (language), encyclopedia, and more.
PaperRater.com is an online service you can copy/paste 1800 words to check for spelling, grammar, readability, and more (free) They charge a fee if you want to scan more than 1800 words.
Editing and revising your writing is the stage towards publishing I like the least. It requires less creativity and more writing savvy to craft the plot, characters, settings, conflict, and sentence struction to wow a readership.