These web apps look interesting, and I use some of them.
Writers, this web page has plenty of links that will capture your interest.
At his excellent blog, Trevin wrote a post about book proposals to publishing companies. His post is helpful, especially because he recommends the book Thinking Like Your Editor.
Theologian John Frame is well known for his books The Doctrine of God, The Doctrine of the Knowledge of God, The Doctrine of the Christian Life, and–most recently–The Doctrine of the Word of God.
Here, he offers wise remarks on how to write a theological paper. Thanks, Justin Taylor, for the link!
“Don’t use words too big for the subject. Don’t say ‘infinitely’ when you mean ‘very’; otherwise you’ll have no word left when you want to talk about something really infinite.”
–C. S. Lewis
“If you’re afraid you can’t write, the answer is to write. Every sentence you construct adds weight to the balance pan. If you’re afraid of what other people will think of your efforts, don’t show them until you write your way beyond your fear.
If writing a book is impossible, write a chapter. If writing a chapter is impossible, write a page. If writing a page is impossible, write a paragraph. If writing a paragraph is impossible, write a sentence. If writing even a sentence is impossible, write a word and teach yourself everything there is to know about that word and then write another, connected word and see where their connection leads.”
The book How to Write Clearly, by Edwin Abbott, was published in 1883 and is now available online for free here. I skimmed through it, and it looks profitable. I imagine, though, that not all of his rules are considered as pertinent now, but, again, I only surveyed the book.