Social Publishing or Article Directory

Hi Group,

I’m wondering what plugin or theme might enable wordpress to be able to be a shared blogging platform. The idea being something like squidoo or hubpages whereby a user can sign themselves up, submit an posting, have categories, and allow visitors to leave comments and/or rate the posting?

Seems like a plugin with this feature set could be a natural extension of wordpress but I am hard pressed to find anything.

Thanks.
tom