IUCR:

www.iucr.org - International Union of Crystallography

it.iucr.org - International Tables

http://journals.iucr.org/ - Crystallography Journals

http://checkcif.iucr.org/ - CheckCIF

http://www.iucr.org/resources/cif - Everything you ever wanted or needed to know about CIFs.

http://www.iycr2014.org/ - International Year of Crystallography

Associations:

http://www.amercrystalassn.org/ American Crystallographic Association

http://crystallography.org.uk/ British Crystallographic Association

http://www.aps.org/ American Physical Society

http://www.acs.org/ American Chemical Society

Software:

Databases:

Miscellaneous:

X-ray Anomalous Scattering  http://skuld.bmsc.washington.edu/scatter/AS_index.html

Space Groups: http://ressources.univ-lemans.fr/AccesLibre/UM/Pedago/physique/02/cristallo/espace.html

Temperature Calibration - http://www2.fkf.mpg.de/xray/html/temperature_calibration.html

ALS X-ray Data Booklet - http://xdb.lbl.gov/

PRODRG2 - http://davapc1.bioch.dundee.ac.uk/cgi-bin/prodrg

Point Group Symmetry Visualizer - http://symmetry.otterbein.edu/gallery/