I have used soapUI (http://www.soapui.org/) extensively for the past few years for basic integration testing of WCF (with basic endpoint bindings) and SAP web services. I've been using those also to test out connections to my current client's back-end banking systems.
soapUI isn't perfect though - as there are differences in interpretations of the WS-* standards between the Java and the .NET worlds - and soapUI is based on a Java stack. One such problem that you'll find with calling Microsoft WCF services with wsHttpBinding soapUI is that you get the following exception when you use the default settings:
This is because there is no "To" entry in the header of the message. The fix for this is to go to the soapUI WS-A tab and ensure that the "add default wsa-To address is checked on" as per the screenshot below:
s:Sender a:DestinationUnreachable The message with To '' cannot be processed at the receiver, due to an AddressFilter mismatch at the EndpointDispatcher. Check that the sender and receiver's EndpointAddresses agree.