This tool has been around for a long time but I had never seen it until somebody showed me at a client site the other day.
.NET WebServiceStudio 2.0 (download) lets you invoke webmethods from WSDLs without writing any code!
Update - Since GotDotNet was closed down, the above links are broken. This is an alternative version:
For example, try this location web service. If you enter a US ZIP code, it will return the City.
http://webservices.imacination.com/distance/Distance.jws?WSDL

One Comment
wsstudioexpress has never been updated and it still can’t invoke a web method.
Check this one out instead:
http://codeplex.com/storm