Through a comment on a blogpost by Nancy White I found this article about a virtual community using a discussion list (listserv) in combination with a wiki. The wiki serves as a collaborative repository. You can access the article here if you want to read it in full.
I've been advising a community where using an online discussion forum where few people had experience with a wiki. We started a wiki to put knowledge products together. Though it was hard to get people to work on the wiki, it was very attractive to some because of its structure as compared to the discussion forum that may look very chaotic. So I'm a little jealous that the community in this article has such an active wiki process. But it does provide a clear picture of what's possible!
The community is a help-based community discussing the applied use of CSS, hence a technical topic. The interesting part is the analysis of how the wiki helps with the social processes of keeping the conversation on-topic and avoiding holy wars. Because the email list is a push technology and the wiki more a pull technology, more off-topic discussions can be allowed on the wiki than on the mailing list, hence it provides a space to address wider needs. Holy wars are redirected to the wiki and because members are forced to summarize their arguments into an information product, the wars are used more constructively.
The wiki also has helped in the process of retaining the old members. It helps to introduce new people by having a place to redirect them when they pose 'old questions' that have been discussed before. As a result, the questions on the mailing list can remain focused on new problems. The wiki also worked to attract new members because people find the wiki and become interested in the mailing list.
By the way, CPsquare is organising a conference about wikis for communities. You can track the resources by following http://delicious.com/tag/waatwaat.