I found this website whilst searching for a catalog/atlas for objects fainter than (about) 13th magnitude - seemingly the limit for most planetarium software. The question, I was trying to answer was: How do I determine the magnitude of very dim objects in a long exposure image.
Apart from an online search facility which can provide detail on small areas of sky, there are links to books and software which can be ordered via Wilmann-Bell's e-commerce site. The only downside is that their freight charges are a bit steep, dollar-wise.
Interested members can check out the site at:
http://www.usno.navy.mil/USNO
Allen