How to select high quality structures from the Protein Data Bank?
There is a very nice database, pdbcull (also known as the PISCES server in the literature). It filters the PDB for high resolution and reduced sequence identity. It also seems to be updated regularly. Depending on the cut-offs, you get between 3000 and 35000 structures.

If you are specifically interested in rotamers, you may want to look at top8000 instead, where they have checked for high resolution, and good MolProbity scores. They also provide a rotamer database.

PDB also provides their own clustering. They first cluster the sequences, and then extract a representative structure for each one, based on the quality factor (1/resolution - R_value). This has the advantage of being comprehensive, but you will have bad structures when no good ones were ever obtained.