One of the current discussions in emerging/missional/fresh-expressions-of church concerns the tension between "missional communities" - that go out to reach the wider community in which they are located - and "attractional congregations" - that invite the wider community in to their Sunday services. In our experience, there is a tension, but it can be a creative one.
The model we've worked to develop here in Sheffield is one of three sizes of community within the church, which we see as reflecting various sizes of community in both Old and New Testaments, as well as in anthropological studies of many different cultures. In our experience, many other churches have the "small group/cell/house group" and the larger "celebration gathering" but the middle size - historically the congregation in the English setting (as opposed to the home and the cathedral), the size that has great missional potential, being small enough to share a common vision and large enough to do something about it - is missing. We've found that being part of three sizes of structure, that fit inside each other, to be effective - each size having its particular strengths and weaknesses.
Jo and I have been gathering a monthly celebration (around 200-300 people) of several missional communities for the past three years. Tomorrow is the last time we'll meet together. It's the last time not only for us, because we are leaving, but for everyone in this particular structure, because particular structures are not set in stone and exist only for seasons, of variable lengths depending on the life-cycle of the church. That dynamic, organic growth and change is evidence of life - including the death of seeds required for harvests to grow. This past three years - and indeed the five-and-a-half years I've been on the team at St Tom's, and the fourteen years I've been part of this church/these churches - has been a great adventure. But as we prepare to move on, we are confident that God has greater things in store - for us, and for those we leave behind.