Key Concepts
Term of Art
Program-to-Program
Large-Grained
Loose Coupling
[Mostly] WWW-Based
Standards-Oriented
XML-Based
Discussions
Microsoft overview of the concept: http://msdn.microsoft.com/webservices/understanding/readme/default.asp
Sun discussion of building web services using java: http://www.theserverside.com/resources/article.jsp?l=WebServices-Dev-Guide
Sun discussion of similarities and differences between their Java-based and MS's .Net approaches: http://www.theserverside.com/resources/article.jsp?l=J2EE-vs-DOTNET
IBM vision of the future of Web Services for its own systems: http://www-3.ibm.com/software/solutions/webservices/pdf/SummitEnd2end.pdf
W3C discussion of various scenarios for using web services: http://www.w3.org/TR/2002/WD-ws-arch-scenarios-20020730/
Oracle white paper provides a good general overview of the concept, with (expected) emphasis on their products: http://otn.oracle.com/tech/webservices/pdf/webservices_twp.pdf
Macromedia architect talks about their view of web services in an interview: http://www.infoworld.com/articles/hn/xml/02/04/29/020429hnlynch.xml
Entry point for discussions of BEA's web service views and products: http://www.bea.com/products/webservices/index.shtml