The Writing and Revision Stylebook - Handbook on how to write winning essays, with advice on editing, grammar, spelling, and revision. - http://www.cooperhill.com/
Writing the News - Walter Fox's guide to the style and structure of newswriting for beginning journalists. - http://www.netreach.net/~wfox
Writer's Bookcase - How-to-write books for creative writers, books for writing crime, romance, fantasy, travel, editing. - http://www.writersbookcase.com
Get It. Write! - A concise, 32-page book that simplifies grammar and writing skills. - http://www.getitwrite.com/