This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
I'm not sure that you need any web services specific notation on the use case diagram level. Text-based/goal-oriented use cases tend to be more useful anyway (see: Use Cases) and no special notation is required. Example: Web service use case: Travel reservation