Today, I bring two sources for grammar.
The first is University of Illinois’ Center for Writing Studies online grammar handbook. The program is geared more towards non-creative writing, but there are some useful tips, and grammar is grammar.
The second is an online publication of Strunk and White’s The Elements of Style. If you have looked at any list of suggested readings for writers, this book is on it. It is made available, for free, through Bartleby.com which houses numerous literature and reference publications.
May the Muse be with you,