My colleague Tara Miller has a book out on small groups called Finding the Flow. If any of your churches are working on this area, I suggest you check it out.  Far from taking a programmatic or model-based approach, this book works just as well for missional groups as it does for more traditional small groups.  Best of all, she and co-author Jenn Peppers share some great, down-to-earth stories that tell group life like it is—messy but fraught with the potential for transformation.