www.ginkoapp.com → awesome writing tool
www.zotero.com → citation management
www.citationmachine.net → good tool to make a quick citation
www.overleaf.com → awesome LaTeX collaborative writing tool
Installing some grammar-check app could help and of course regularly reading the Uni-edit writing tips, as well as maybe some industry websites, such as Teacher Eddy, GrammarLabs, and JournalGuide, etc. as they all provide useful content freely available online.
I think http://professorpublish.com/ might be useful for researchers.