Crystallography courses on the web

X-ray Crystallography in 5401 seconds (Manfred S. Weiss): http://www.embl-hamburg.de/~msweiss/teach (A very short and simple introduction)

The book of Fourier (Kevin Cowtan): http://www.ysbl.york.ac.uk/~cowtan/fourier/fourier.html (Nice explanation of what is important in a Fourier calculation)

The physical meaning of the phase in crystallography (Stanley C. Nyburg): http://www.ccp14.ac.uk/maths/nyburg/ (A Classic in Crystallographic Teaching)

Crystallographic movies (James Holton): http://ucxray.berkeley.edu/~jamesh/movies (Very illustrative movies on the effects of resolution, R-factor data completeness etc. on the information content of the structure).

Crystallography 101 (Bernhard Rupp): http://ruppweb.dyndns.org/Xray/101index.html (Very good and nice introduction, some interactive parts)

Crystallographic Tutorials (Michael R. Sawaya): http://www.doe-mbi.ucla.edu/%7Esawaya/tutorials/tutorials.html (good for beginners, somewhat outdated when it comes to programs)

Basic Maths for Protein Crystallographers (Eleanor Dodson): http://www.ysbl.york.ac.uk/~mgwt/CCP4/EJD/bmg/index.html (If you want to work in protein crystallography, here are the math essentials)