I took an online class to learn spiral quilts from Renae Merrill. They are foundation pieced and look very cool. Here's a link to her gallery -
http://www.ranaemerrillquilts.com/gallery/Spirals
I'm glad I learned the technique, but don't plan to make a full quilt. I did use one of my blocks from the class as the top of an insulated casserole carrier.