  The amount of data produced by large observational facilities and space
missions has led to the archiving and on-line accessibility of much of this
data, available to the entire astronomical community. This allows a much wider
multi-frequency approach to astronomical research than previously possible.
Here we provide an overview of these services, and give a basic description of
their contents and possibilities for accessing them. 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 our attempt to keep the
report as complete and up-to-date as possible will inevitably be outdated
shortly. We will endeavor to maintain an updated version of this document
on-line.
