In the past, I've always found the IUCr crystallographic pamphlets to be useful when teaching diffraction. They've reorganized their website to make their educational resources easier to find. On this link, you can find the IUCr teaching pamphlets, a short description of how to grow crystals,  and other crystallography web resources.

 Teaching Pamphlet Topics

• 1. A non-mathematical introduction to X-ray diffraction
• 2. An introduction to the scope, potential and applications of X-ray analysis
• 3. Introduction to the calculation of structure factors
• 4. The reciprocal lattice
• 5. Close-packed structures
• 6. Pourquoi les groupes de symétrie en cristallographie
• 7. Crystal structure analysis using the 'superposition' - and 'complementary' - structures
• 8. Anomalous dispersion of X-rays in crystallography
• 9. Rotation matrices and translation vectors in crystallography
• 10. Metric tensor and symmetry operations in crystallography
• 11. The stereographic projection
• 12. Projections of cubic crystals
• 13. Symmetry
• 14. Space group patterns
• 15. Elementary X-ray diffraction for biologists
• 16. The study of metals and alloys by X-ray powder diffraction methods
• 17. An introduction to direct methods
• 18. An introduction to crystal physics
• 19. Introduction to neutron powder diffractometry
• 20. Crystals - a handbook for school teachers
• 21. Crystal packing
• 22. Matrices, mappings, and crystallographic symmetry
• 23. Teaching crystallographic and magnetic point group symmetry using three-dimensional rendered visualizations