Of late, left and right I have been running into portals and folks talking about portals. Problem is, everyone seems to be talking about something different from the next person.
In most instances the GIS analyst community is talking about portals in terms of a gateway to geospatial data and services, ala the Geospatial One Stop (GOS) portal, whereas some GIS developers are instead talking about portlet-based geospatial applications, and some are talking about varying combinations of the two, drawing on the portlet-based implementation of the GOS2 version versus the ESRI GIS Portal Toolkit (GPT)...
Even when we are talking about portlets, the discussion varies, with competing platforms like IBM Websphere and Oracle IAS even running side-by-side within the same enterprise, though with different applications. Sure, people suggest that Java-based portals and the JSR-168 standard for portlet-to-portlet communications make things interoperable, but the realities are still far from concrete. At risk of incurring the wrath of the Open-Source J2EE community, I have to say that even these have their not-insubstantial issues when it comes to platform, infrastructure and interoperability. Thank the Gods for XML and Web Services.
So in the meanwhile, portlet-based implementations of slick or robust GIS applications may not yet be there.
I think portals and portlet development have come a long way, but I think a true fusion of GIS, AJAX and SOA is still to come from intrepid developers.