Dynamic taxonomies integrated into e-learning tools play a double role: on the one hand they are a powerful retrieval system in the usually large content base of an e-learning environment, on the other hand they allow and strongly encourage orthogonal visits of available learning resources by exploiting associations the user would not have thought of (and which are the specific contribution of dynamic taxonomies). These two roles are of interest both for teachers, who may use the search engine to retrieve hints for presentations, assignments, etc., and for students, who may explore the whole learning environment in a new profitable way, which makes, for example, immediately available for a same subject different aspects dealt with in different courses. In the paper we describe the integration of dynamic taxonomies into Moodle, a Course Management System for cooperative learning.