The amount of data produced by large observational facilities and space missions has led to the archiving and on-line accessibility of much of these data, available to the entire astronomical community, and allowing a much wider multi-frequency approach of astronomical research than previously possible. Here I intend to draw attention to these services, to give a basic description of their performance and ways of accessing them, with special attention to the situation at IAC. Apart from services providing observational data, many of those providing general information, e.g. on addresses, bibliographies, software etc. are also described. The field is rapidly growing with improved network technology, and my attempt to keep the report as complete and up-to-date as possible will inevitably be outdated shortly. Further editions are hoped to keep the report actualized.