Group blog – Communication in the Admin

Just looking to get an established blog expanded to include more writers. Thus I’m looking for a plugin that allows for good communication among writers on the backend. I know I saw one before, but I can’t seem to relocate it.

What I want, is to list some story ideas, send basic notes back and forth between writers, or at the very least have a “notepad” time space that we can leave notes to eveyone.

THoughts? Any plugin’s being used out there that you would suggest?