One of the best sources of information about crystallization is in the
technical support pages of Hampton Research Tech Support.
The crystallization pages of Terese Bergfors provide excellent
tutorials as well as a pictorial library of crystallization phenomena.
101 from Bernhard Rupp is
a great on-line introduction to X-ray crystallography.
Heavy Atom Database, HAD for heavy atom derivatives used in isomorphous replacement phasing.
HIC-Up, the Hetero-compound Information Centre - Uppsala