At the end of my inorganic course, I teach several "cool" spectroscopic techniques that inorganic chemists use. These techniques are discussed within the context of bioinorganic chemistry, and I typically cover EXAFS/XANES, X-ray crystallography, EPR and Mössbauer.
This website introduces (or reviews) Fourier Transforms in a neat graphical way, but most importantly, illustrates the phase problem. Given the intensities from your crystal and the phases from your model, the phases are more important! Which is too bad, as we don't have ready access to that information.
After using these web resources, a student should have an appreciation for the "phase problem" in X-ray crystallography and a better understanding of the importance of good modeling.
I really like the graphical approach to the phase problem illustrated by Cowtan. I run through some of the introductory FT pages and then the "duck" and "cat" illustration of the phase problem, followed by the "manx cat" illustration. The students gain quite an appreciation for model building without having to actually build models or work with diffraction data.