There is probably a huge amount of good stuff available from the people who are working actively with XmlRpc, Biztalk and other approaches to web services. More too from XML writers such as [http://uche.ogbuji.net/uche.ogbuji.net/ Uche Ogbuji], who has put much good stuff on IBM's developerworks site, among other things.
Sadly nobody has categorised or classified it in the Wiki, so at the moment we have to scratch around.
What do you mean by web client programming? Are you talking about making a WebBrowser? Or writing WebServices? WebProgramming? DistributedProgramming?
I highly recommend the FindPage.
We have pages on XmlRpc, BaseHttpServer, DocXmlRpcServer, ...
...just trying to get a feel for what you are looking for.