Useful Links
Structure visualisation
external page Vesta is a powerful free of charge structure visualisation program. Most useful for inorganic structures.
external page Mercury is a commercial structure visualisation program distributed by CCDC. The free version has reduced functionality, but is still very powerful. Most useful for organic structures.
external page CrystalMaker is a commercial visualisation program with a lot of add-ons. Most useful for inorganic structures.
Single crystal structure refinement
external page Shelx is THE standard for single crystal structure refinements.
external page Olex provides a nice interface to shelx and offers a lot of additional tools for visualisation and more. Free of charge software with some commercial add-ons. Highly recommended for organic structure refinement.
external page Jana is the best choice for modulated structure refinements and other non-standard average structure refinements (neutrons, electrons, magnetic structures, etc.).
Powder diffraction
Widely used and free software for Rietveld refinement and other powder diffraction data evaluation are external page Fullprof and external page GSAS
The most popular commercial powder diffraction programs are external page Topas and external page Highscore Plus