Call it what you will - the adaptive, composite, on-demand, networked enterprise. Any way you slice it, that *kind* of company is about not concentrating on non-core competencies, but instead being able to focus on *results.* And I think its a key driver in the world of SaaS...
Along those lines, I'm exploring some companies that could help build the "composite" enterprise:
Salesforce.com - to manage sales leads, CRM (every one knows this)
Bryght - for my website, wiki, blogs
DemandWare - an on-demand ecommerce platform (tailored to multichannel commerce)
EchoPass - SaaS-driven contact and call center management
AppStream - SaaS-driven application deployment for enterprise IT
ExactTarget - Saas email solutions (marketing)
intacct - SaaS ERP
NewsGator - SaaS-driven enterprise RSS solutions
Qualys - SaaS based IT security
...Throw in a benefits provider (i.e., Trinet) and i've just assembled probably over 70% of what I need to run a good sized (50-250 person) company....
And I never installed software......;-)