This document summarizes a special issue of the International Journal on Digital Libraries focusing on recent applications of Knowledge Organization Systems. It includes an editorial introduction and 6 full research papers covering topics like improving interoperability using vocabulary linked data, aligning conceptual structures in controlled vocabularies, composing hierarchical relations, a sharing-oriented design for networked knowledge organization systems, representing gazetteers and period thesauri in space-time, and extending the CRM for documenting standing buildings.