The Centre de données astronomiques de Strasbourg (CDS) provides homogeneous access to heterogeneous information of various origins: information about astronomical objects in Simbad; catalogs and observation logs in VizieR and in the catalogue service; reference images and overlays in Aladin; nomenclature in the Dictionary of Nomenclature; Yellow Page services; the AstroGLU resource discovery tool; mirror copies of other reference services; and documentation. With the implementation of links between the CDS services, and with other on-line reference information, CDS has become a major hub in the rapidly evolving world of information retrieval in astronomy, developing efficient tools to help astronomers to navigate in the world-wide ``Virtual Observatory'' under construction, from data in the observatory archives to results published in journals. The WWW interface to the CDS services is available at: http://cdsweb.u-strasbg.fr/