OpenSource MicroBlogging

I have been given a book to read about Social Media and one called Twitter Power. I am beginning to think that Twitter is not something I can ignore any more.
I am not yet convinced that I need an account but I think I should be informed about how it works and how the system of communication can be used.

I was wondering today what our office communication might look like if we were to use a twitter like tool to announce office news or meetings and tasks completed. So I took a look at OpenSource options. Because in an office environment we already have the community created but we don’t want the world to follow our office “tweets”. Here is what I found:

Automattic Came up with a solution for their office in 2008 and released it as a theme for wordpress. They call it P2.

The only other thing I could find in the OpenSource community was I have not looked into either of theses to see how they work or compare with twitter.