Michael Frost has this new book coming out, which I'm sure will be a must read if you enjoyed his previous co-authored book.
I've written before about 'The Shaping of Things to Come', by Alan Hirsch and Michael Frost. A hugely influential book, and Emergent hosted them on a tour in the UK in late 2004. I wrote some thoughts and critique of their thesis and suggestions here.
Out of the many configurations of emerging church, Frost is in the radical sociology area, ie. the reconfiguring of the place and ways we do church, more than the theological. It will be interesting to see how he maps things further in this book.