Many good ones with searchable data, and useable interactive interfaces, e.g.: Protein Data Bank: http://www.rcsb.org/ GenBank : http://www.ncbi.nlm.nih.gov/Genbank Molecules 'R' Us: http://molbio.info.nih.gov/cgi-bin/pdb *But*, very few that allow non-interactive (i.e. programmatic) access to the data they contain (a couple had started to use BioCorba)