Discovery of things as well as their resources, metadata, properties, and capabilities is a fundamental requirement in any Internet of Things (IoT) ecosystem. This paper analyzes the state of the art of communication technologies for the IoT with respect to discovery functionalities. Therefore, a comprehensive study of the technology landscape on IoT discovery mechanisms is provided. As a key contribution, we introduce a novel categorization of the available discovery technologies. Further, we identify and analyze the generic interaction pattern of each category. Finally, the technologies of each category are evaluated. With this evaluation at hand, IoT system designers are given decision making support. In the future, this analysis will serve as a basis for a generic discovery framework for the IoT. This work has been elaborated as part of the W3C Web of Things interest group.