I have used a few wikis in the past in my school. Last year as a school we used a wiki in order to write our school's mission statement. It allowed the entire faculty to have input but gave us the flexibility to do it on our own time. We did not have to constantly meet and discuss what we wanted to say. It also allowed up the ability to go back and review previous posts.
This year instead of forcing my teachers to make a time for a meeting during the day, I would like to set up collaboration wikis. I think it would be a great way to brainstorm ideas and share them not only with the teacher I am currently working with, but also allow other teachers to see what we have done and are doing together in the library. Since collaboration is such an important component, I believe this will not only provide all of us the flexibility to work together, but also give us a chance to provide that input for each other, even if it is in the middle of the night (when I tend to have the best ideas ... and not always a great time for a meeting!). It is also a great way to document this collaborative effort.