I am looking for a webapp that has
- OpenID authentication
- Allows users to share information in private groups
- An administrator( a group leader) who controls who is present in the group
- Allows the administrator to share feeds so that every person in the group can read and comment individually
- UI similar to Google Reader or any similar feed reader.
This app might look like too localized requirement. Please flag the question in case if it does not fall into this site's scope.
I want to know how information is shared across a group of people in an organization like 50-100 people. The only reason I am looking for a webapp is I personally do not prefer emails and email groups.