I just posted on the Association Renewal Blog about Ram Charan’s article in HBR about a big culture change at Home Depot. The AR post is more about the "change" part (what got you there won’t get you where you’re going).
But there’s also a good quote in the article about the "culture" part:
A cultural transition can be achieved systematially, even under less than favorable conditions, not simply through the charisma of the person leading the change but through the use of mechanisms that alter the social interactions of people in the organization.
Culture lives in interactions. That’s why you can’t legislate it, or turn it around by putting up inspirational posters on the wall. You have to have a deep knowledge of the social interactions in your organization, and through interactions you discover the change.