The number of available bioinformatics resources is overwhelming. The most critical issues met by scientists are (1) to identify the resources suitable to express their protocols, and (2) to compose them in an executable workflow. Many advanced projects offer solutions to the composition of services in a workflow, while others address the interoperability of services. We present an approach that allows the organization of bioinformatics resources in a scientifically meaningful framework that leverages existing effort on interoperability and workflow composition and execution. We present ServiceSemanticMap, a system that allows users to explore the wide availability of bioinformatics resources organized with respect to an ontology. The user interacts with the system through a graph-based interface, discovering the resources by exploring the graph. The system exploits a resource catalog where providers may register their bioinformatics tools through a Web resource entry form. We demonstrate the approach with a semantic map devoted to structural bioinformatics. Our approach is collaborative: a group of experts develop and maintain the ontology, while providers and users may register new resources.