I'm interested in the use of analytics and metrics in community management. I have some experience in working with community managers of free / open source software communities to find out which kind of information is useful in this task, and how it can be retrieved from the repositories where it lives.
Among the kind of information that seems useful, for instance, you can find metrics about the general activity of the community, details about who is entering, leaving or changing their activity pattern (eg, increasing participation above a certain threshold), the age (as time in the project) of the persons in the community, and the attraction and retention rates over time, etc.
i think it will be interesting to discuss about which metrics you're using or would like to use, stories about how those metrics are collected and used, and even about the general usefulness (or lack of) of analytics and metrics in community management.
Disclamer: I'm working with a company producing free / open source software for analyzing software development repositories, and have been researcher on the field for some time, but I'm not a community manager (well, maybe an aficionado community manager, but not more than that). This said, I have some experience in the problems of community management, and how to detect and track them.