This is an extremely useful webserver which will run your structure through various programs. It will check for violations, calculate the RMSD (overall and ordered regions only) and run it though a variety of structure validation programs such as the Protein Data Bank Validation Suite, Procheck, ProsaII, MolProbity and Verify3D. Definitely use this site during your structure calculation stage and before submitting a structure to the PDB.
This program will analyse your restraints for their information content. It will show up restraints which have a large effect on the structure and/or which are not supported very well by other restraints. You should probably be very sure of such restraints before leaving them in your calculation. It uses up a lot of CPU time and the calculation of Iave(how well supported is each restraint by others) is best run on a cluster.
This is a new program for NMR protein structure validation which can be run on the iCING server.
This is quite a large software package which is actually meant for modelling, but it includes a range of structure validation tools. Although the program can be run locally, it is probably best to use the webserver. Be aware that some of the databases used for these may not necessarily be very up-to-date. You may get worse Z-values than from some of the PSVS programs. The algorithm to investigate atomic clashes also differs from those used by the PDB and MolProbity.