This great article from Information Week gives an overview of the benefits of using Wiki technology to enable collaboration within the enterprise: How To Use Wikis For Business.
But they fail to mention what I consider the best all-around Wiki software -- Dokuwiki.
Here is how the author of DokuWiki describes the software:
DokuWiki is a standards compliant, simple to use Wiki, mainly aimed at creating documentation of any kind. It is targeted at developer teams, workgroups and small companies. It has a simple but powerful syntax which makes sure the datafiles remain readable outside the Wiki and eases the creation of structured texts. All data is stored in plain text files – no database is required.
DokuWiki is PHP based. It lets you include other PHP code or HTML pages on the fly, meaning you can embed an external web report in an intranet web page that you create on the fly. Very powerful!