We want something which is JSR-168 compliant, and preferably is just a web portal, not a content management system with a portal build-in.
Liferay - Liferay is designed to deploy portlets that adhere to the Portlet API (JSR 168). Many useful portlets are bundled with the portal (Mail, Document Library, Calendar, Message Boards, to name a few) and can be used as examples for adding your own custom portlets.