When building the patient API we've been using Fiddler for debugging and testing of the REST protocol. Here's a screenshot showing testing of the PUT method using JSON.
Our SOAP testing application is built as a Windows console application in VS2010. Feel free to download our SOAP Testing Client using the link below and use it as a starting point for your implementation. If you have used web services via WCF before, then this should look familiar. A key item to pay attention to is the CustomMessageInspector.cs, which is responsible for inserting the API Key into the header.Download