Antioch University's Staff Training and Support Wiki is very good I thought. The Front Desk Training and Policy Pages are full of detailed, useful information, everything from working the telephone system to watering the potplants. It seemed that information was easy to find, something that is not always true of the policies and procedures at my workplace. Of course the ease of use depends on someone having ultimate control of the wiki to ensure the information is correct and up to date.
The Montana History Wiki had alot of links to information held elsewhere. It seemed to help people locate and access information rather than actually holding the information on the wiki site. No point in re-inventing the wheel.
I could imagine that we could use wikis here at the library to allow access to policies and procedures, also to discuss upcoming events such as the Seniors Trip without a million phone calls/emails between the staff involved. However any Wiki would need to be well controlled to prevent it degenerating into a confusing maze of pages, threads etc with no order to them. I have just added some comments to the WA Public Libraries Web 2.0 Basics Home wiki, and I must say it seems to be a fairly random assortment of comments and pages. It is just a training page to show the basics of how to edit a wiki, but it already shows how disorganised a wiki could become without adequate supervision.