1. At a computer system including a processor and a memory, in a computer networking environment including a plurality of computing systems, a method for providing an intermediary service configured to provide system functionality processing on received service requests and to determine which registered services are to be used to process the requests, the method comprising: an act of an intermediary service receiving registration information for one or more available services provided by a plurality of service providers, the registration information including information identifying various types of functionality provided by each of the service providers' available services, the registration information being used to register the available services with the intermediary service; an act of the intermediary service intercepting a service request from a client computer system identifying a type of functionality that is to be performed by at least one of the available services provided by the plurality of service providers that are registered at the intermediary service, the service request further including rules indicating how the identified type of functionality is to be performed and further specifying one or more groups of users or computer systems to which the rules apply; an act of the intermediary service determining which of the one or more registered available services is configured to provide the type of functionality requested by the client, wherein each of the service providers' registered services is configured to provide service-specific settings for one or more generalized services that are to be performed by the intermediary service, the service-specific settings corresponding to the specified rules; an act of the intermediary service sending the processed service request to the service provider whose service is determined to provide the type of functionality requested by the client, such that the determined service provider sends the requested service to the intermediary service to provide the functionality requested by the client, wherein upon sending the requested service to the intermediary service, the determined service provider further includes an indication of one or more generalized services that are to be provided by the intermediary service in addition to the identified service determined to be configured to provide the type of functionality requested by the client, wherein the identified service specifies one or more specific settings indicating how at least one of the generalized services provided by the intermediary service is to be performed; upon the intermediary service receiving the requested service from the determined service provider, an act of the intermediary service performing the one or more indicated generalized services on the service according to the settings specified by the determined service provider for that generalized service; and an act of the intermediary service providing to the client computer system the requested service which includes both the determined service provider's service as well as the one or more indicated generalized services provided by the intermediary service provider.