Squonk and I have been getting all excited about Terry Lee Hale of late. Hale is an american singer/songwriter/picker who plays a lot of fingerpicked stuff with and without a slide. He's one of those guys who spends a lot of time away from standard tuning though, as Squonk notes, he sounds much more "american" than, say, Martin Simpson.
So anyhows.... here are some notes by Mr Hale (a true deviant who first learned to play in drop D and then moved on to open D) about the whys and hows of open tunings.
http://www.terryleehale.com/guitars/opentunings.html
