Techniques are described for facilitating interactions between computing systems, such as in accordance with usage models that are configured for available services by the providers of the services. In some situations, the services are Web services, and an electronic Web service (“WS”) marketplace is provided via which third-party WS providers make their WSes available to third-party WS consumers who purchase access to those WSes via the electronic marketplace based on configured usage models selected by the consumers. Some or all of the one or more usage models configured for an available WS may each have associated use prices and/or non-price use conditions, and if so access to those WSes using those usage models may be provided only if a consumer requesting access provides appropriate payment and otherwise satisfies the specified use conditions for a selected usage model.