How can churches use Social Media as part of their ministry and outreach? I am not going to answer that for you ... but knowing your audience — who uses Social Media — may help you answer the question within your local church context.
Check out these statistics from 2013 about Social Media usage and growth: http://www.jeffbullas.com/2013/09/20/12-awesome-social-media-facts-and-statistics-for-2013/
Let us know how you are using Social Media within your church.