It's from SometimesCrafter blog. She has a tute on PP too, which is nice for those who haven't done that yet.
I have made several blocks now and still love it. Only work on it for a couple hours at a time, though. My friend is also making it. Neat pattern for use of smallish scraps. I can see it in scrappy plaids, polka dots, everything!! Here's the link:
http://www.sometimescrafter.blogspot...ing-block.html