(Education First) These pages are a complete English grammar guide filled with the rules of English usage. Each grammatical rule is explained in plain English with several examples, and when needed, counter-examples.
(Quick and Dirty Tips) An award winning website provides a collection of tips to improve your writing. It covers tricky punctuation, grammar rules, and word choices, striving to make grammar fun rather than frustrating.
(Purdue University) This Online Writing Lab (OWL), maintained by Purdue University, provides writing resources and instructional material covering all aspects of writing and citing research papers.
(POWA) Covers many topics associated with writing from beginning through advanced. Site developed by Chuck Guilford, professor emeritus at Boise State U and author of Beginning College Writing.
(University of Wisconsin-Madison) Part of The Writing Center, University of Wisconsin – Madison, which contains tools for successful writing, including citation help.