When I worked at the Health Sciences Library I used our wiki as both a staff training and a resource tool. I placed all of our circulation, reserves, holds management, policy, etc. documents and manuals on the wiki so that staff could have immediate and searchable access to them. The library as a whole used the wiki to share common documents and to help communication with a number of projects that involved many different departments.
At NCSU, I am using our ADS wiki much the same way. I have a small group of staff who are working on building our department wiki which will contain all of our training manuals, emergency procedures, contact information, etc. Once we have it built and seeded, we are going to have wiki training so that everyone feels comfortable editing and contributing content.
I wrote an article about this that is coming out later this year.
It details the HSL experience and some tips and ideas for using wikis in libraries. Email me if you want a rough draft.