What is the Church?
Francis Chan on the Church
There is a lot of material by Francis Chan on Rethinking Church
Letters To The Church
The Mission of The Church
In the belief that, at its heart, the mission of the church is to make disciples of Jesus Christ, the material on this topic is on that site.
That is not to say that making disciples is the only thing that churches and Christians should do but it is primary. We make disciples who then respond to God's call on their lives to seek justice, care for creation, love their neighbours etc.