Liferay Portal is a free and open source enterprise portal written in Java. You can use it for building business solutions that deliver immediate results and long-term value. It is primarily used to powerful corporate intranets and extranets portal.

Liferay Portal comes in two versions: Community Editon (CE) and Enterprise Editions (EE). Liferay Portal integrated Web publishing and content management, shared Workspaces, enterprise collaboration, social networking , enterprise portals and identity management.

With profile authorization, adminstrator & users can define which information can be viewed. Social networking features help the company creating local communities, user groups & they can have their own mini portals.

Other features are: wikis, accounting, instant messenger, calendar,forums,  webmail, blogs & more.

Runs PHP, Ruby, Python, Grails and other lightweight scripting technologies.

Website: http://www.liferay.com/
Demo: http://www.liferay.com/request-a-demo
Download: http://www.liferay.com/downloads