Grammar Handbook -- Handbook by the Writers' Workshop, University of Illinois at Urbana-Champaign that explains and illustrates the basic grammatical rules concerning parts of speech, phrases, clauses, sentences and sentence elements, and common problems of usage.
Guide to Grammar and Style --
A miscellany of grammatical rules and explanations, comments on style, and suggestions on usage created by J. Lynch, Rutgers University.
Writer's Handbook --
Produced by the Writing Center at the University of Wisconsin-Madison, this site offers an excellent collection of concise instructional materials for university students and instruct