John Hartford, just because he ain't been mentioned yet. He had a unique point of view, to say the least.

John Stewart was at least as good a writer than he was a singer/personality. He wrote so many songs that the gems are still, for the most part, not recognized.

If I had to pick one, it would be Gordon Lightfoot. But then, Ian Tyson and Steve Goodman would probaly be there some days. And Chris Hillman is almost criminally under-appreciated as a writer, and then...