It's been interesting to explore some of the uses libraries are making of the wiki format. Wikis seem especially suitable in the context of a community of some kind, and it's interesting to see public libraries using them in some of the examples provided.
I have been involved for about a year now in a wiki created by a group of education liaison librarians at QULOC universities. We found it necessary to meet and do some groundwork first, to establish a framework to give a structure to the wiki, which people can now contribute to.
Our wiki is aimed at a particular public, and for a particular purpose: it's aimed at student teachers, and is intended to be a place where they can find and share web resources which are using for prac teaching in schools. It's called Prac Resources Wiki. It's growing nicely.
Wikis seem well suited to staff intranets; staff directories (e.g. UQ Contacts) which allow self-updating; sharing recommended best practice; identifying and sharing resources.