Shared controlled vocabularies are a prerequisite for collaborative annotation and semantic interchange. The creation and maintenance of such vocabularies is, however, time-consuming and expensive. The diversity of research questions in the humanities makes it virtually impossible to create shared controlled vocabularies that cover a wide range of potential applications and satisfy the needs of diverse stakeholders. In this paper we present a novel conceptual approach for mitigating these problems. We propose that projects define their own vocabularies as needed and link the vocabulary terms to one or more concepts in a reference thesaurus, so that the project-specific term effectively serves as a "label" for a set of shared concepts. We also describe the implementation of this approach in the Labeling System. The Labeling System is a Web application that allows users to easily import concepts or create SKOS vocabularies and link the vocabulary terms to concepts from one or more reference thesauri.