The CLARIN Concept Registry (CCR) is an OpenSKOS instance, which implements the W3C SKOS recommendation and data model. It can be accessed via https://www.clarin.eu/ccr/
Currently it is filled with many concepts from for example the EAGLES project, various metadata initiatives and hopefully other sub-disciplines and initiatives. The national CLARIN Concept Registry Coordinators take care that the registry is not too fragmented and meets a number of criteria.