In the last years, we have witnessed the growing use of web technologies and e-learning systems in the direction of the collaborative paradigm. The number of educational resources and environments where is possible to share digital resources is rapidly increasing and nowadays the Web offers great opportunities to students, teachers and instructional designers in order to design personalized learning paths. Given this scenario, the author carried out a biennial research project on “e-learning and innovative educational technologies” and analysed different ontological models, technologies and standards for designing learning resources. In this book, he introduces several descriptive models of learning objects, such as controlled vocabularies, metadata schemes, taxonomies, thesauri, and ontologies representing instructional resources features. For each model, a brief description is provided with a focus on those elements that are more relevant from a pedagogical perspective, in particular for learning content design.