Willow Creek Community Church

Willow Creek in a suburb in Illinois is one of the largest church in America with 20,000 attending each week. (In the spirit of full disclosure, I should mention that more than a decade ago, I was a member and youth leader in the church.)

From Wikpedia:

http://en.wikipedia.org/wiki/Willow_Creek_Community_Church

An analysis of its organizational dynamic:

http://religiousmovements.lib.virginia.edu/nrms/superch.html