SoapUI is an open source web service testing tool which can use xpath for expected result checking. Useful for running scenarios through a webservice. Does not require a WSDL. Supports GUI and Command Line invocation and can be easily evaluated via webstart.
Try exploratory testing of webservices with The Fiddler in reverse proxy mode. Set breakpoints and edit HTTP requests and responses on the fly.
AutoIt (an opensource GUI scripting language) has an IDE based on Scite which makes it really easy to record, edit and run AutoIt scripts.