LifeRay Portal has several fuzzy line boundaries when it comes to cross functionality with Sharepoint and Alfresco. You will just have to check out the live demo and see what features you like better. Sharepoint and Alfresco do Content management better, but Liferay has killer Portal abilities. Sharepoint out does Alfresco in the portal area but is a toss up when it comes to content management. If you like Sharepoint lists, then Alfresco will leave you dry.
Alfresco is the open source content management of choice. For those that do not have an affinity for Microsoft, you can roll your own for free at Alfresco.com or signup for one of their support packages and supported/tested releases. You call the shots on how much you want to support it.
Microsfot Sharepoint is now mainstream, if you have not reviewed what it can do for departmental collaboration, I would advise you to do so now.