Community based multisite examples

I am looking to build a site using a wordpress network the would be community based, so I would like to implement features such global tags, recent posts network wide ext on the frontpage/main site.

I look at wordpress.com and edublogs.org both seems to be more i guess I would call it service oriented, the sites and more focused on selling their "service" and don't seem to have much as far as community features. I'm not saying that's a bad thing, it's just not what I am going for.

I would appreciate any community oriented multisite links anyone can share to help inspire me in building my own and give me some good idea's.