The Puget Sound Guitar Workshop is outstanding, not just for songwriters, but for acoustic folk/blues/swing musicians of all sorts. Highly recommended!

I also recommend a book by Natalie Goldberg called Writing Down the Bones, published by Shambhala. Natalie's method is what she calls "writing practice": give yourself 10 or 30 or 60 minutes to write, write anything, keep your hand moving, don't edit while you're writing, stay with original detail rather than abstractions, forget your self, just write, just write. Then go back and find the gems, or take that energy and jump right into your song or novel or poem or whatever. I've been reading that book over and over since 1987, and I never get tired of it.

Another gem from Natalie: "When you sit down to write something, give yourself permission to write the worst junk in the world." You have an infinite amount of words and music in you: if you don't like what comes out this time, keep writing and you'll find something else.

Aloha,
Mark