You'll find quite a few good references for these and similar matters that I've assembled at http://asiapac.com.au/Links/WebServices.htm or at its mirror/backup site http://notestracker.com/Links/WebServices.htm
You could do worse than start with a nice and succinct article from BEA recently published (03 April 2006) ... SOA: Are We Reinventing the Wheel? in which Nick Simha asks "What is a service?" and examines the hype around Service Oriented Architecture, looking at CORBA, DCom, J2EE, Web services and the new kid on the block, service infrastructure.
And there's another good one also well worth a read: it's by Steve Bennett (also from BEA) ... Successfully Planning for SOA: Building Your SOA Roadmap which offers a concrete plan, along with tips and insights, to help you build an effective SOA roadmap and to help ensure the success of your SOA initiative.
UPDATE - 09 May 2006:
In his Edge Perspectives weblog, John Hagel has just written an interesting article: SOA Versus Web 2.0? in which he says:
... a cultural chasm separates these two technology communities, despite the fact that they both rely heavily on the same foundational standard - XML. The evangelists for SOA tend to dismiss Web 2.0 technologies as light-weight “toys” not suitable for the “real” work of enterprises. The champions of Web 2.0 technologies, on the other hand, make fun of the “bloated” standards and architectural drawings generated by enterprise architects, skeptically asking whether SOAs will ever do real work.John had earlier asked if we are Ready for Web 3.0? -- which is getting ever closer to my concept of "Web Pi"
UPDATE - 20 May 2006:
Lawrence Wilkes at CBDI Forum has just penned an article about Top Ten Traits of the Successful SOA Organization
UPDATE - 06 June 2006:
Macehiter Ward-Dutton have just published some germane comments on all this stuff: SOA 2.0? Stop the madness (including some pointed comments about the IT industry analyst "profession").
UPDATE - 24 July 2006:
Steve Jones has an interesting blog about SOA and related topics. A couple of his postings are: Shooting the myths of SOA and How SOA helps you hit the agile sweet spot ... and (in case you really thought you knew what "reliable messaging" and all that "WS-*" alphabet soup is) this post: WS-RM, WS-RX, Reliable Messaging which is what?