Want to do a sample web service application(SOAP based) for practice.Please suggest an example..

For learning purpose, I want to create a sample web service using SOAP. I created the Hello world service which is good to begin with but now I want to do some sample application for better practice.For web frameworks a common sample application would be shopping cart e.t.c but for webservice on searching the internet i got only hello world examples. Any sample application of intenet or Please suggest what can be a small sample application for self practice of webservice(and concepts like wsdl etc).

Thanks