I've been looking at information on creating interoperable web services as well as tools, and came across these resources.

Articles & Online Books

• Building Interoperable Web Services: WS-I Basic Profile 1.0
• Interoperability Notes on Apache Axis 1.1 and Microsoft .NET Framework 1.0/1.1 FAQ
• Application Interoperability: Microsoft .NET and J2EE 
• Web Services Enhancements 1.0 and Java Interoperability, Part 1
  See how the WS-Security specification can be used to securely sign Web service calls between Microsoft .NET and Java using the IBM Web Services ToolKit.  
• Web Services Enhancements 1.0 and Java Interoperability, Part 2
  In part 2, continue to explore how the WS-Security specification and implementation can be used to securely sign Web service calls between Microsoft .NET and Java.

• WS-I Implementation Tools
  "..a targeted set of tools to help practitioners verify that their Web services are compliant with industry standards and implementation guidelines."
• GotDotNet Web Service Tools
  - r2d tool
  - DeDoc tool
  - WebServiceStudio 2.0
  - Direct Internet Message Encapsulation (DIME) Validator
  - WSDL Verification tool
  - WSDL Browser tool
• YATT (Yet Another Trace Tool)
  "YATT is a project to replace the current proliferation of trace tools ( tcpTrace, proxyTrace, pcapTrace ), with a single extensible tracing tool. YATT features a new GUI built with WTL, complete with a Hex View mode, and currently ships with 2 Trace providers, one based on WinPCAP and one based on the W2K Raw sockets support. "
• SoapScope 3.0
  "A toolkit-independent Web services diagnostic system for examining, debugging, testing and tuning Web services."
• OmniOpera & Omniopera Viewer Plug-in for Internet Explorer
  "Omniopera is a WSDL and XML schema editor. The Omniopera Viewer is a free plugin for Internet Explorer® that provides an easy to understand summary of WSDL and XML Schema documents. Check WSDL schema validity and verify that all QNames resolve. Hyperlinks allow you to drill in for details, all the way back to the W3C schema-for-schemas if you need to. "
• WsContractFirst
  A Visual Studio .NET Add-In for improved 'Contract First' Web services development. Ever wanted to simply right-click on a WSDL file in Visual Studio .NET and generate code from that Web service contract? Now you can - whether it be a client-side proxy class or a server-side stub skeleton: you choose. The Add-In automatically determines the project's programming language and accordingly generates source code (currently C# and VB.NET supported).