EAI is my most interesting topic off late as my experience is mainly in this area. I started off with the Big Brother IBM's Websphere Portal server where I first learnt of a Portal application and what collaboration means.
I witnessed the Enterprise Application Integration to its fullest when I was onsite where I saw an architecture with IBM Websphere Portal being the Kep player and Fatwire Content Server, eTrust SiteMinder, Sun LDAP servers, Lotus Notes Sametime server and Google's Search Engine are integrated to the Portal collaboratively to offer the user with a Rich set of features in a single site.
Well as i was all good words and praising IBM all the way I was put into another architecture where Vignette Portal server forms the Key and Vignette Content Management, Autonomy Search Engine, Microsoft Exhange Server and Sun LDAP servers are integrated collaboratively to offer the same set of features for an intranet environment.
And Now I am dusting my hands on MOSS 2007 and its features for EAI and you may see most of my views on MOSS 2007 and comparing it with the earlier said EAI environments.
As you can see my Footer down there, these are just my views and are limited to the perspective of what I see or learn from the resources that I have access to.