This article presents a general framework for building conceptbased digital course libraries. The framework is based on the idea of using a conceptual structure that represents a subject domain ontology for classification of the course library content. Two aspects, domain conceptualization, which supports findability and ontologies, which support reusability of learning resources are incorporated uniformly in the library architecture. The suggested framework implies a layered information structure of the library content consisting of three layers, each capturing a different aspect of the information space - conceptual, resource-related, and contextual. We present an environment, TM4L (Topic Maps for Learning), aimed at supporting the development and use of concept-based digital course collections. The new ISO standard, XML Topic Maps (XTM), that provides a paradigm for organizing, retrieving, and interchanging information on the Web, is used in the proposed framework to implement concept-based digital course libraries. (Contains 4 figures.)