CRYSTALLOGRAPHY - G. Chapuis, Laboratoire de Cristallographie, Ecole Polytechnique Federale de Lausanne, Switzerland Multimedia Crystallography Course (Text, Images & Applets). VERY VERY VERY...EXTENSIVE.

Examples of Crystallography Course Chapters include
"...Introduction;
Symmetry of Crystals;
Structures of Crystals;
Diffraction Principles for Periodic Objects;
Diffraction Methods;
Resoultion of Crystal Structures..."

Link: http://escher.epfl.ch/eCrystallography/