In this paper, the notion of a smart service community is proposed to address the grand challenge of a huge number of the Internet-of-Things (IoT) devices providing similar services in a smart city environment (e.g., parking, food, healthcare, transportation, and entertainment). We propose that a smart service community be built as a cloud utility accessible via a mobile application installed in user-owned IoT devices, such as smartphones. The cloud utility provides cloud-based interfaces, including registration, service satisfaction reporting, recommender credibility reporting, and service recommendation, with the goal of recommending the best service providers based on a user's specified service performance criteria. The trust-based service management techniques, utilizing the IoT-assisted technology, are developed to automatically measure service ratings and recommender credibility ratings, and compute one-to-one subjective trust scores to allow a user to select the best service providers among all. The feasibility of the proposed approach is demonstrated over contemporary service ranking systems using a smart food service community for which the major performance metric is the service wait time.