Drupal's focus on social publishing can help you create sites and applications to help your users express their opinions and engage with one another.
Drupal has a robust point-and-click permissions system that gives you the flexibility to organize and distribute administrative and content access rights. You can have tight control over your user types’ abilities to create, view, administer, and otherwise interact with content on your site. You also have the ability to leave content private and publish it only when it's ready, and with the Workflow module, you can change the steps needed for content to become public.
Organic Groups module makes it easy to foster collaboration, giving site users the ability to create public or private working groups. Distributions such as Open Atrium and Drupal Commons can help set up your organization or group with a Drupal-powered collaborative website in a matter of minutes.
By integrating with systems provided by the OpenID module, Facebook Connect module, and LDAP module (Lightweight Directory Access Protocol), you can make sure that your users don't need yet another login to contribute to your site.
Open Atrium has out-of-the-box collaboration built in for project teams.