A method, system, and computer-readable medium is described for facilitating interactions between computing systems, such as by providing an electronic Web service ("WS") marketplace via which third-party WS providers make their WSes available to third-party WS consumers who locate and purchase access to those WSes via the electronic marketplace. Some or all available WSes may have associated use prices and or non-price use conditions, and if so access to those WSes may be provided only if a consumer requesting access provides appropriate payment and otherwise satisfies the specified use conditions. In some situations, WS consumers may also purchase subscriptions to provide later access to registered WSes. This abstract is provided to comply with rules requiring it, and is submitted with the intention that it will not be used to interpret or limit the scope or meaning of the claims.