I've been working with Web services in an academic setting for quite a while now, but there's one basic aspect about them that I do not get. Here it is:
Assume you have an application that you want people to use as a Web service. So you make (or most likely generate) a WSDL description for it and adapt the application so that its functionality can be invoked by somebody having access to that WSDL description. You now have a fully functional Web service. But how do you actually let people know where to find it and what it represents?
I am aware of the UDDI initiative, but imho that has already started to fail. It doesn't even make that much sense to have EVERYBODY publish their Web services in one place, and the big companies backing it up seem to have realized that. So what options do you have left? How can you tell people "Hey, check out this nice Web service API I made for you. Here are the WSDL files too.". Do you just make links to the WSDL descriptions on your Web page?
Write some documentation and examples for it, and publish them along with links to the service on a/your website. That's all there is to it.
Here's an example of a good documentation website:
http://code.google.com/apis/maps/documentation/webservices/index.html