What a treasure trove of advice I've rediscovered! The first advice that comes to mind is Elmore Leonard's essay for the NYTimes series "Writers on Writing". A complete archive of that column can be found here. I believe writing advice is as personal as shopping advice: if it doesn't fit your style, you're not going to pay attention to it. I want my writing to be the spare, pointed, hooptedoodle-lacking writing Elmore Leonard is encouraging, and so I take his advice. (Blogging is different, this is more like chatting to strangers.) But his advice might not fit you, which is why you should read through that archive; I know I'm planning to.
I also take the advice of Bird by Bird: Some Instructions on Writing and Life by Anne Lamott, because even if I don't remember everything she says, that core concept is comforting - we all have to begin somewhere, and might as well take it bird (word) by bird (word). Though I read this before grad school, I believe it was suggested or required reading for a course or two, and so I enjoyed it again, along with Stephen King's On Writing: A Memoir of the Craft and Aspects of the Novel by E.M. Forster, books I'm not sure I would have picked up had it not been for classes Writing I & I. 
Some of my favorite books on writing are actually for children, most notably Avi's A Beginning, a Muddle, and an End: The Right Way to Write Writing, illustrated by Tricia Tusa. This book is a sequel to The End of the Beginning: Being the Adventures of a Small Snail (and an Even Smaller Ant), which, while not about writing, does make some clever commentary about the nature of books and fables. As extra prizes for the Odyssey Book Shop's annual children's writing contest last year, I had the pleasure of handing out both A Beginning, a Muddle, and an End and another book on writing for children, one about the more technical aspects, entitled Spilling Ink: A Young Writer's Handbook by Ellen Potter, Anne Mazer, and illustrated by Matt Phelan. Both present encouragement and advice for aspiring young writers.
Just at the time I began writing this post, I discovered two more books about writing I need to look through. One, How Fiction Works by James Wood, has been compared to E.M. Forster's work mentioned above, but the second is the one I'm most interested in. Off the Page: Writers Talk about Beginnings, Endings, and Everything in Between is a compilation of authors' input marketed as a "literary tell-all". Edited by Carole Burns, with an introduction by Marie Arana, authors are quoted under section titles such as "Haven't I Seen You Somewhere Before?: How Characters Come to Life", "All That Jazz: Playing with Language and Style to Suit the Story", and "Good Writers Borrow, Great Writers Steal: The Writers Whom Writers Love and Why". The list of authors includes Tobias Wolff, Colm Toibin, Art Spiegelman, Marisha Pessl, Tim Parks, Joyce Carol Oates, Walter Mosley, Alice McDermott, Andrea Levy, Jhumpa Lahiri, Edward P. Jones, E. L. Doctorow, Michael Cunningham, A. S. Byatt, Russell Banks, and Paul Auster to name a few.What books about writing inspire you?
