What I do for almost every site with multiple authors:
- Create a separate blog for meta discussions, for example
meta.example.com
. - Use P2 as theme.
- Install Authenticator to allow access for members only.
- Install something like Inform about Content, so the members get an email whenever something new was posted. I probably wouldn’t do that for 300 members …
You could write a dashboard widget with the newsfeed for the meta blog like the Incoming Links and make it a MU Plugin to set it active on every new blog.
This works rather good; it requires almost no configuration, and even people with low technical skills understand it fast.