Portal Software was perceived as the Next Big Thing to enhance collaboration within a company back around the turn of this century.
End of an Era - for Portal Software
Today, in Aug05 the last remaining significant vendor, Plum Tree, is being swallowed by BEA.
Accoring to a Butler Group blog, recent events has been predicted years ago. Whilst one can always find an abundance of Bulls Eye hind-sight analysis, should people have dismissed predictions of boom/bust in specific software industries?
Jun05 Plum Tree product strategy can be seen at portalsmag.com 
One year ago, Plum Tree CEO John Kunze said this about their product:
"We have been planning for this (Service Oriented Architecture) role. Our core engine and infrastructure can consume Web services in massive scale and deploy them in massive scale to very specific audiences."
"Plumtree offers its administration and orchestration of services (also) in interactive collaborative applications."
A Gartner view of Portal Software dated 2004 can be seen at portalsmag.com
Supplanted by Microsoft Way???
It is too much of a coincident and not long after the takeover of the "struggling" Plum Tree, Microsoft is making available an "experimental" Portal Software start.com site at start.com . This September Zero Five preview use terms like "gadgets" that are identical to ones for Plum Tree addons.
Microsoft MSN developer web site suggested Ajax Web Applications possibilities and wrote:
"Start.com is now extensible, with our new AJAX framework. Go to the Start.com developer site to learn how to build your own gadgets, customize your feeds, and more."
Using portal to enhance collaboration
Big Blue has this marketing paper which could be applicable to the general topic of Portal Software. -> www-5.ibm.com
they suggested it is an enabling technology for Organizational Cultural Transformation (not just Cultural Change).
see also Wiki Portal
See original on c2.com