A good writer has a strong tool box. Here are some of the resources I keep in mine.
On the Craft of Writing
The Anatomy of Story, John Truby
The Moral Premise, Stanley Williams
Plot and Structure, James Scott Bell
Self-Editing for Fiction Writers, Renni Browne and Dave King
The Plot Thickens, Noah Lukeman
How to Grow a Novel, Sol Stein
Websites
Helping Writers Become Authors
Kristen Lamb
The Book Designer
Sondra Kraak 