GUI Tool for working with Web Services

soapUI is a free and open source desktop application for

• inspecting Web Services
• invoking Web Services
• developing Web Services
• Web Services Simulation and Mocking

Functional, Load and Compliance testing of Web Services
It is mainly aimed at developers and testers providing or consuming Web Services (Java, .net, etc). Functional and Load Testing can be done both interactively in soapUI or within an automated build or integration process using the soapUI command line tools.

http://www.soapui.org/