Creating Short Fiction---Damon KnightWell written and informative.
Characters and Viewpoint--Orson Scott Card
Elements of Fiction Writing SeriesComplex but worth it.
Building Fiction--Jesse Kercheval
Humorous, snappy, and well done.
On Writing Science Fiction---Former Editors of Isaac Asomov's SF Mag.
Excellent book, if a bit dated.
Steering the Craft---Ursula K. LeGuin
Working my way through this one slowly. For singles or groups, with some great exercises. She's smooth as glass.
Bird by Bird---Anne Lamott
A ride through both the heaven and hell of writing by a remarkable writer. It's funny and sad and inspirational.
Scene And Structure---Jack Bickham
Elements of Fiction Writing series.
Plot---Ansen Dibell
Elements of Fiction Writing Series