Plugin for Collaborative Workspace?

hi

I’m setting up a blog which I plan to have about 7 different bloggers/authors help write content for.

However the blog is on a certain topic, so I want some way in which the authors can quickly collaborate in the admin section to decide or notify others of what they will be writing about. (as I want to avoid having posts on exactly the same thing)

Any plugin recommendations for something like this?

cheers
nathan