The online repository for protein sequences is the ExPASy Molecular Biology Server. The online repository for 3-D protein structures (determined by x-ray crystallography, NMR, etc.) is the Protein Data Bank .
Insofar as I know, there is no convenient listing of proteins without an experimentally determined 3-D structure. Your best bet is to find a protein in the ExPASy files and then check the PDB to see if there is a structure available. Trust me, a little bit of hard work never killed anyone. :)
You may also want to take a look at the http://metallo.scripps.edu/ at Scripps if you're interested in that sort of thing.