One Nomad points toward Enterprise Portals Suites Review
Standards-based portals are a must. If the product complies with portal standards, such as WSRP (Web Services for Remote Portlets) and JSR (Java Specification Request)-168, and Web services standards (SOAP, WSDL), you're assured that third-party products will work with it and the applications you develop will work with your existing infrastructure.
Custom applications are the most difficult to include in a portal, but the most sought-after. In the past, developers had to learn platform-specific portal APIs. The massive push toward an SOA (service-oriented architecture) has let portal vendors embrace both Web services standards and portal-specific ones. With these standards, the vendors can offer technology that lets even nontechnical users build custom applications.
Indeed, the goal for many companies is to create complex portals that include composite applications without writing a line of code. Application developers can concentrate on business logic and functionality rather than learning platform-specific APIs or even coding new interfaces to existing applications.
Soon the entire Federal government will be required to conform to open standards, follow developments at the XML community of practice.