The PDB-REDO databank contains optimised versions of existing PDB entries with electron density maps, a description of model changes, and a wealth of model validation data. It is a good starting point for any structural biology project.
All the entries are treated with a consistent protocol that reduces the effects of differences in age, software, and depositors. This makes PDB-REDO a great datatset for large scale structure analysis studies.
Here you can find more information about downloading PDB-REDO databank entries.