Robert K. Greenleaf is the author who popularized the concept of "servant leadership" in the business world--at least for those who didn't know the concept originated with Jesus! His book
Servant Leadership: A Journey into the Nature of Legitimate Power and Greatness (Paulist) is a collection of his lectures, articles and essays on the topic of servant leadership. Though not written specifically for church leaders, it will be a valuable resource for those who read it.