See this post on using wikis for an Intranet in healthcare. Wiki software is getting good enough these days that the look-and-feel is now tolerable for an Intranet.
Many years ago (1999) .. in a galaxy far, far away .. I built an Intranet home page that was butt-ugly, but it got the job done, and I was trying to spread the concept of an Intranet as a useful tool for clinical and administrative tasks.
Alas, that page still adorns the Intranet there (though it doesn't run from a server under my desk anymore, thankfully!) and while progress is being made (the www site was recently revised – though usability experts would likely give it a C+ at best) .. while I have moved on to other places.
.. and one of the most successful projects at CapitalCare was the re-building of the Intranet as a Wiki. It was fun and challenging and I can take credit for only planting the seed and evangelizing a bit. Watering, fertilizing and nurturing were well managed by a great team of colleagues.