this post was one of the two that were listed regarding SOAPI.
For a full overview of the SOAPI eco-system see What is SOAPI and why should I care?
For a more robust API discovery tool hosted in Silverlight see Soapi.Explore (silverlight)
All parameters are documented, and as much as is practical, are validated and/or assisted with appropriate input elements.
SOAPI-EXPLORE (Dead site) is always up-to-date and in sync with the API.
SOAPI-EXPLORE (Dead site), select 'save target as...'. All done.
Comments, suggestions, complaints, praise and adulation can be registered here or via email to SOAPIWATCH@skysanders.net.
Keep an eye on http://soapi.info/ for all things SOAPI. ;-)