Here is the site of Bethany Reynolds (it says she originated it).
http://bethanyreynolds.com/what%27ssnw.html
There is a tutorial for the Stack n Whack on the site and other info. There are also several books with SnW patterns.
http://www.amazon.com/s/?ie=UTF8&key...l_9d8uriylpa_b
You can't have too much info.