X-Ray Diffraction Facility of the MIT Chemistry Department
International Union of Crystallography (IUCr)
American Crystallographic Association (ACA)
Kevin Cowtan's Tutorials: Interactive Structure Factor Tutorial, The Book of Fourier, etc.
Mike Sawaya's Tutorials: Crystal Characterization, Molecular Replacement, MAD/SIRAS Phasing, Graphics, etc.
Crystallography 101 by Bernhard Rupp
Twin Refinement with SHELXL by Regine Herbst-Irmer
High Resolution Protein Refinement by Thomas R. Schneider
Refinement of Disorder with SHELXL by Peter Mueller
Escher Web Sketch by Wes Hardaker and Gervais Chapuis