Holy Conversations is a good resource for strategic planning. It's very flexible, i.e. adaptable for specific needs, as well as simple. I read through it once, and am now reading it with a small group of leaders. We'll discuss the basic concepts and determine the scope (and length) of the planning process. Part of the discussion will be funding and use of an outside facilitator.
I'm also reading Good to Great by Jim Collins. It is based on research with for-profit corporations, but the findings can easily be transferred to organizations in general: it all boils down to identity, context, purpose, and relationships.