Drupal - Open Source CMS - content management platform

Drupal is an open source content management platform licensed under the GPL. Equipped with a powerful blend of features, Drupal can support a variety of websites ranging from personal blogs, corporate brochures and large community-driven websites

Some of the Features are ...

Collaborative Book - Our unique collaborative book feature lets you setup a "book" and then authorize other individuals to contribute content.

Role based permission system - Drupal administrators don't have to tediously setup permissions for each user. Instead, they assign permissions to roles and then group like users into a role group.

Blogger API support - The Blogger API allows your Drupal site to be updated by many different tools. This includes non-web browser based tools that provide a richer editing environment.