I've been writing a collection inventorying system for myself, in anticipation of the coming streampocalpyse (which could take several forms), and I've been fru

I've been writing a collection inventorying system for myself, in anticipation of the coming streampocalpyse (which could take several forms), and I've been frustrated and dismayed by the state of UPC Data sources, especially free ones. OpenLibrary is the one good source I've found. Any others?