I hacked ChatterBlock v3.1 so that it will work as a center block.
I also added some controls in the ChatterBlock Admin to turn the center block on and off, to make it show on all story pages or just the home page and allow you to select where on the page the chatter will be displayed; top of page, after the featured story or bottom of the page.
See it in action here ->http://www.sillig.com
Download it from here ->http://www.sillig.com/filemgmt/index.php?id=1
Copy the files from this archive over the existing files of your working ChatterBlock 3.1 installation.