The excellent article by BITKOM (Bundesverband Informationswirtschaft, Telekommunikation und neue Medien e.V.) is unfortunately in German (click here http://www.bitkom.org/de/themen/36129_61111.aspx), but summarizes the three current Cloud layers into Software as a Service (SaaS), Platform as a a Service (PaaS), and Infrastructure as a Service (IaaS). The article is one of the best down-to-earth summaries with actionable recommendation and check lists that I’ve read so far, but it does treat the Cloud as a commodity, as a plentiful resource. The danger, however, many articles from Mashable or ReadWriteWeb fall into, is to write about “unlimited computing power”. Throw in a bit of misunderstood Chris Anderson’s “Free” or “zero-cost of digital distribution” (while it is actually near-zero-cost plus a bunch of other smart things that people tend to quote out of context, or even worse, quote out of a review about a review of Anderson’s books), and you would have no market anymore:
http://www.playoutintelligence.com/2009/09/cloud-economics-saas-paas-iaas/
An excellent (German) article by BITKOM summarizes business challenges, decision points, and business models of cloud-based solutions. BITKOM segments the “Cloud” space into Software, Platforms, and Infrastructure. While this is all true and good for current business, the Cloud stack looks more like Information, Relationships, Services, Platforms, Infrastructure, and Networks.