Dictionaries
The Compact Oxford English Dictionary is a one-volume reproduction readable with an included magnifying glass. It’s not your everyday dictionary, but it’s a valuable, exhaustive reference.
The New Oxford American Dictionary suits routine use.
Style manuals
The classic Elements of Style is illustrated by the delightful Maira Kalman in this unforgettable edition.
APA style is found in the Publication Manual of the American Psychological Association.
AP followers use The Associated Press Stylebook.
The Chicago Manual of Style
GPO style is outlined in the Style Manual: an Official Guide to the Form and Style of Federal Government Publishing.
A Manual for Writers of Research Papers, Theses, and Dissertations is widely used in academia.
The Elements of Legal Style
Words into Type is an all-purpose style manual.
General usage
The Columbia Guide to Standard American English
The New Fowler’s Modern English Usage updates the original Fowler’s for contemporary writers.
Garner’s Modern American Usage
Writing and grammar
Several Short Sentences About Writing is a revelation for anyone who wants to write with grace.
Spunk & Bite uses wit, plenty of examples, and exercises to improve writing skills.
The Elements of Grammar
Sister Bernadette’s Barking Dog is a charming tutorial on how to diagram a sentence.
Editing
The Elements of Editing
Trade associations
Editorial Freelancers Association
Society for Editors and Proofreaders
American Translators Association