Ok, so this might be called something more univeral, since UPC codes are only part of the many total barcodes used to identify physical object types. But 'universal product code' and product identifiers is what I mean to write about, so it will do.

There are a few billion products in the world. They should be noted and recorded in a public database - at least those that are publicly distributed and sold. I don't need to know all about the secret products or byproducts that are still given codes for use in internal evaluations and process reviews. I might need a way to identify the hundred thousand things in my personal space in terms of where they came from, what they contain, and what else is like them or where to get more information or replacements.

• http://www.upcdatabase.com/stats.asp - stats from one public db of 1.1M UPC records, entered by hand and from uploaded databases. would gladly take in more user-generated UPC info.

  http://www.upcdatabase.com/itemform.asp - low traffic lookup form from the above

• http://www.ean-search.org/perl/ean-search.pl?q=5099750442227 - European Article Number. search 2.7M entries.
• http://www.booksprice.com/ISBN13.jsp - ISBN to UPC converter
• http://www.adams1.com/issn.html - ISSN for magazines.

• http://www.adams1.com/faq.html#upclist - an FAQ from which some of the other sites were found.
• http://www.barcodesinc.com/generator/index.php - barcode generator from code!

Global info : the business end

• http://gepir.gs1.org/V31/xx/ - GS1 broken into categories. offers a 'GTIN' search which may encompass the others above/below

  http://gepir.gs1.org/V31/xx/gtin.aspx?Lang=en-US - searches any product that may be invoiced, priced, or exchanged in any supply chain