I like Andrew Jones. He's a missionary who's been around for ages, and probably has the most complete history of the emerging church movement (blogged, not in a book).
I'd like to draw a few quotes from him, firstly from Emerging Church Movement (1989 - 2009)?:
"In my opinion, 2009 marks the year when the emerging church suddenly and decisively ceased to be a radical and controversial movement in global Christianity. In many places around the world, the movement has already been either adopted, adapted, or made redundant through the traditional church catching up or duplicating EC efforts."
"In 2009, the emerging church either grew up, stopped being offensive, switched gear from experimental to normal, became the new mainstream, or a bit of each."

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Roger Saner's blog: Journey
Graeme Codrington: Regeneration