My favorite non-denomination is the Calvary Chapel movement, which arose at the beginning of the Jesus Movement in the late sixties/early seventies. When I was living in Texas, I would sometimes attend the Wednesday evening worship service at Calvary Chapel Austin. This movement was started under the pastoral leadership of Chuck Smith (one of my heroes), formerly of the Foursquare denomination.
Calvary Chapel churches are structured so that the full authority for church business and decision-making is given to pastor, who is also the head of the church board. This is often referred to as the "Moses model" of church government. Christianity Today has an article about how this leadership structure is causing major problems in one of the largest churches in the country.
Calvary Chapel has also begun a new bureaucratic structure, called Calvary Chapel Outreach Fellowships, that looks an aweful lot like the denominationalization of this anti-denominational non-denomination.
When I get worn down with the top-heaviness of the United Methodist Church, I often daydream of being a part of a structure closer to Calvary Chapel's structure. Its healthy for me to see that sooner or later there have to be systems put in place for financial accountability, credentialling, and quality control even among those who have tried hard to avoid such a structure, and did so successfully for a long time.