A portal is a web application which typically gathers content from different sources and supports personalization of content.
JetSpeed is a portal server which you use to deploy your portlets, which will eventually form part of a web portal. Most portal servers provide built-in portlets and support features (security, integration with external systems) which help quickly develop web portals. So, JetSpeed does help you to quickly develop a web portal.
OpenCMS is for web content management, which helps you to quickly knock out a website (not a web portal).