How-To Geek has published a nice article on creating your own Twitter style group blog using P2 WordPress theme. They cover how to setup P2 on both WordPress.com, hosted service, and using the WordPress.org self-hosted version.
“A group blog theme for short update messages, inspired by Twitter. Featuring: Hassle-free posting from the front page. Perfect for group blogging, or as a liveblog theme. Dynamic page updates. Threaded comment display on the front page. In-line editing for posts and comments. Live tag suggestion based on previously used tags. A show/hide feature for comments, to keep things tidy. Real-time notifications when a new comment or update is posted. Super-handy keyboard shortcuts.”
Read article at: http://www.howtogeek.com/howto/21373/create-your-own-twitter-style-group-blog-with-p2/
Theme homepage: http://p2theme.com/