Crystallography (Chemistry)
Bragg's Law and Diffraction 
This is a nicely done short description on Bragg's law and its use in determining atomic structure of crystals. There is a well done applet and some good examples of experimental diffraction patterns to help with the understanding of Bragg's law.
X-ray Crystallography 
This short review is more geared towards protein crystal growers. There is a very basic intro to crystallography and then some info on how to grow crystals. It is well written and easy to understand.
