Stewart Mader put together a list of 5 Effective Wiki Uses over at Website Magazine.com:

1. Project Management
2. Customer/Client Collaboration
3. Documentation
4. Online Community
5. Policies, FAQ, Guidelines and Best Practices

Here at The Firm we currently have four uses for wikis:

First, we are using them as a classic encyclopedia, similar to the Wikipedia model.  We start a wiki page for a substantive legal topic, seed it with information and ask others to edit and add to the information.  It is easy to link a topic page to other related topics.

Second, we are using the wiki as a lightweight content management tool.  We are replacing hard-to-edit conventional web pages with wiki pages.  This use is largely focused on administrative information that can be edited and updated by those who know and are responsible for the content.  We are removing the barrier of having to go through IT or an intranet editor to update their content. The individual subject matter experts can update the information themselves.

Third, we are using wikis to manage clients.  Rather than keeping a client’s practices and procedures manual in a word document or three-ring binder, we “wikify” it.  The individual sections of the manual get their own wiki page in the wiki library.  Also, each case/matter for the client gets a separate wiki page in the wiki library.  On the case/matter’s wiki page, we maintain the status of the matter, with key notes and items to be completed.

Fourth, we use wiki pages to manage administrative projects.  Each project gets an wiki page. On that page we list the items to be done, the milestones to be achieved and the links to other relevant information.  On the page you can get a background, see how the project has evolved, where it is headed and its current status.  This works much better than a folder full of e-mails.