Because the branch managers have been considering developing a wiki as a means of updating the Branch Managers' Handbook, I decided to try out Wetpaint. Setting up the wiki was a piece of cake, basically just involving three steps. I've set it up as needing invites so I'll be adding some of my colleagues as writers if we decide to go in this direction for our project. My next challenge will be learning how to add the necessary content, but that doesn't look difficult.
I may also try PBwiki, just to compare.