Portals are mainly used in form of internal portals, external portals are relatively rare and prove a big challenge when supposed to work across internal systems. As one of the first steps it is absolutely necessary to achieve a shared definition and wording. Here the example:

So, what is a portal?

A portal is an online application using certain techniques to give
  • Centralized access / single point of entry to
  • Personalized content
  • Integration of users into processes (i.e. selection)
  • Connection and data exchange between heterogeneous applications
  • Targeted at certain groups of people

And what does a portal do?

Main functions of a portal are
  • Connection, categorization
  • Search over most or all integrated applications
  • Single sign on and shared user- and user rights management
  • Structuring of processes (who can access what process at what time)
  • Layout
  • Other modules like shopping cart, payment, crm, newsletter, etc.

External facing enterprise portals remain exceptions

Especially in the setting of companies, enterprise portals, customer portals and employee portals are well described. While true customer facing enterprise portals are still not very common, internal facing portals for employee self service and knowledge management are common and can be very cost effective and successful.

Public portals are dead. Public portals are back!

Thoughts on the new portals with social web elements