I like the idea of the wiki, but I agree that there is some fear of others changing lessons — unless it is framed as sharing and adding and improving (that word might be a minefield) onto themed lesson plans. For example, the teacher up the hall might have a neat twist on an existing lesson that you and she (or he) never talked about at lunch. The wiki might provide a space for that sharing.

Blogs are another idea but, I don’t know, most teachers are wary of blogs and are slow to get into the mix (from my experience).

Good luck (and thanks for the two haikus)

Peace
Kevin