CODECS is a collaborative online platform for Celtic studies published by the A. G. van Hamel Foundation for Celtic Studies. Drawing heavily on data management technologies from Semantic MediaWiki and its spin-offs, it accommodates and facilitates a number of resources and resource projects for the benefit of scholars and students of Celtic studies worldwide. By far the most ambitious ongoing project is the *selgā catalogue, a research and teaching tool focusing on annotated descriptions of historical sources (texts and manuscripts) and bibliographic records, with well over 15,000 entries and counting. Behind the scenes, work is being done to refine and extend our annotation mechanisms and improve mappings to controlled vocabularies and indexes. More than offering a simple indexing service, it has evolved to become a mature knowledge management system and data repository. Also of special note is Tionscadal na Nod (modern Irish for ‘The Abbreviations Project'), which serves as an aid to a common stumbling block for those approaching vernacular Irish manuscripts with a mixed feeling of wonder and frustration: how to interpret abbreviations and other peculiar features employed by the scribe. The project stands out as a good example of a project that has managed to solicit the active interests and efforts of volunteering enthusiasts.