Read a succinct, nicely illustrated summary of Web-service protocols in a recent InfoQ article, Making Sense of All These Crazy Web Service Standards. Described are SOAP, WSDL, transport protocols (HTTP/S, TCP, SMTP, UDP, et al), XML schemas, and others that enable messaging across platforms. The article also touches on their interoperability.

Thanks to Pat Patterson, identity architect at Sun, for the pointer in his blog.