Lately, I've been writing ASP.Net Web Services for more than a few projects. With the advent of AJAX and the slow demise of EDI, so much data is moving over the web via XML. With that, comes a need to develop, test and debug those web services. Luckily, there is a great open source tool out there called SoapUI.
I can't tell you how handy this tool is for building Soap requests against those web services. It's helped me unit test my code, helped confirm a production site is online and load test too. Take a look at all of these features. If you don't agree that this is a developer's friend, well... go build your own.