Sites

Crystallography Open Database (COD) (Popularity: )
http://www.crystallography.net
A project accomodating crystal structure atomic coordinates prior to their publication. It is intended to give faster access to the latest structure determinations, openly.

Powder Diffraction File (PDF) (Popularity: )
http://www.icdd.com
maintained by the International Centre for Diffraction Data (ICDD)

Nucleic Acid Database (NDB) (Popularity: )
http://ndbserver.rutgers.edu/
assembles and distributes structural information about nucleic acids.

Metals Structure Database (CRYSTMET) (Popularity: )
http://www.tothcanada.com/
A database of critically evaluated crystallographic data for metals, including alloys, intermetallics and minerals. Contains chemical, crystallographic and bibliographic data together with associated comments regarding experimental details for each study.