How to Write a Novel by Nathan Bransford (this is an ebook that just came out last week, but it’s funny, and full of TONS of great advice)
Invisible Ink by Brian McDonald (He does a lot of work in Hollywood, and has written screenplays, but what he outlines here VERY MUCH applies to any kind of story telling, and he is truly brilliant. There’s also interviews of him talking story around online…I’ll see if I can find them.)
The Art & Craft of Story Telling by Nancy Lamb (I have not read this in a while, but before my first Nano, I read this book, and I still consider the first one my most successful nano. I think although I read this, I was less bogged down by rules and how-to’s and do’s and don’ts than I am now… I don’t know how I would like it in comparison to other things, but I should probably pick it back up, it was great.)
Also, not books, but when I get stuck I go to 2 author’s writing resources/posts on their websites: Sooz’s stuff and Maggie Stiefvaters. Both are really brilliant/invaluable resources to me.
BTW, Sooz, if you ever decided to bundle your writing advice posts into a book: I would TOTALLY buy that. First buyer. 😛