The Knowledge Base Portlet is a portlet designed to allow sharing knowledge within an organization. Some of its features are:

• Create articles using a rich editor, either from scratch or from a template
• Categorize articles so that they are easier to find
• Rate and comment articles
• Manage templates
• Organize articles in a hierarchy to form full guides/books
• Much more...

This portlet is still in development and is planned to be released officially after Liferay Portal v6 is out. If you'd like to be a beta tester or contribute you can follow its development through Liferay's SVN repository.