I'm teaching a writing for children class on Monday so I asked around on a few message boards and here and these are the answers I got to the question about which writing books are your favorite...
Authors choose their favorite writing books:
Dian Curtis Regan Chooses:
Writing Picture Books, a Hands-on Guide from Story Creation to Publication by Ann Whitford Paul
Shutta Crum:
On Writing by Stephen King
Take Joy by Jane Yolen
Story by McKee
Heather Vogel Frederick & R.A. Nelson both choose:
The War of Art, by Steven Pressfield
Rukhsana Khan:
Writing in General and the Short Story in Particular by Rust Hills
Fred Bortz:
The Giblin Guide to Writing Children's Books by James Cross Giblin, and Barbara Seuling's How to Write a Children's Book and Get It Published. I'm partial to Giblin.
Uma Krishnaswami:
I too love the Zinsser book. Also the Worlds of Childhood collection with a forward by him. And for novel-length work there's nothing like Janet Burroway's Fiction Writing. With lots of examples from literary (grownup) fiction but satisfyingly complex.
Barb O’Connor:
Creative Habit, by Twyla Tharp
Ann Stampler:
Bird by Bird by Anne Lamott
Stacy DeKeyser:
On Writing by Stephen King
Susan Patron:
A Literary Life by Carolyn See
Jeanine Atkins:
Writing and Illustrating Children's Books for Publication: Two Perspectives by Berthe Aoss and Eric Suben is one I recommend. There are good quotes, exercises, suggestions for further reading, and they cover the basics well and with more panache than the not terribly exciting title suggests!
For those writing for older children, any collection of Katherine Paterson's essays is bound to inspire, I think.
And me:
The Poetry Home Repair Manual by Ted Kooser
In the Palm of Your Hand: The Poet's Portable Workshop by Steve Kowit