I blogged about Positive Deviance as a change and spread methodology a few months back. It is rewarding to see that the concept is listed in the 8th Annual Year in Ideas Issue of the New York Times Magazine http://www.nytimes.com/interactive/2008/12/14/magazine/2008_IDEAS.html
What I like about PD is it provides a different, yet proven, methodlogy for large scale change that is less "problem" focused. It works on the positive rather than the negative and in my experience is a less stressful and more rewarding improvement process in which to participate.
One of the most famous uses of Positive Deviance is in the reduction of rates of MRSA in a network of hospitals in the USA. Details about this work can be found on the PD website (see below) or for a different perspective you can go to http://www.plexusinstitute.org/complexity/index.cfm?id=3
For more information about PD go to www.positivedeviance.org