For more information on faith development, and other developmental issues for children and youth, see Tracey Hurd's Nurturing Children and Youth: A Developmental Guidebook (Boston: Unitarian Universalist Association, 2005).
The Church of All Ages: Generations Worshiping Together (Herndon, VA: Alban Institute, 2007) edited by Howard Vanderwell and published by the Alban Institute, is a series of essays about different aspects of building multigenerational community in churches. It includes a very good essay by Robert Keeley that summarizes James Fowler's work.
If you really want to dig deep into faith development, James Fowler's classic work on the topic of faith development is called Stages of Faith (New York: HarperCollins,1981) and can be found on most online bookstores.
The Reverend Dan Harper's essay "Learning Types and Their Needs" in Essex Conversations is also a helpful Unitarian Universalist-specific resource.
The Life of John Murray
Two books written by John Murray and edited by his wife Judith Sargent Murray can be found on Google books for free. The first is his autobiography called Records of the Life of the Rev. John Murray and the second is called Letters and Sketches of Sermons. Both offer interesting insight into the life and thinking of John Murray.
Other stories and articles about John Murray can be found at the Unitarian Universalist Association's website. Type "John Murray" into the Google custom search bar and click on "Go" to see what is available.