Mike Amundsen has launched a .NET weblogging service: EraBlog.NET (via the Scobleizer Weblog). I've not had to time to check out the site yet but I did notice that the url for the XML-RPC API when viewed in a browser looks suspiciously like an auto-documentation page generated by XML-RPC.NET. The most recent versions of XML-RPC.NET generate much more informative, and much nicer looking, documentation based on types and descriptive text specified via attributes.
In fact once I extend auto-documentation to handle optional struct members you will be able to describe an XML-RPC interface very well using a .NET interface. Who needs WSDL?
[Speaking of optional struct members I've nearly finished the implementation.]