The Automated Plate Scanner (APS) POSS
Database of the University of Minnesota Group.
The Astrophysics Data System (ADS) Abstract
Service provides easy access to currently about
160,000 Astronomy and Astrophysics abstracts. There is also a european
mirror.
The NASA Image Exchange (NIX):
a new online collection of NASA photographs and images provides a single
point of entry to various photographic databases of six NASA centers.