Amazon Upload - bulk match by barcode. Searches on Amazon for barcode matched products in bulk, you can then upload matched ones in bulk.

You would go to a page which showed all products not on Amazon, you can then select/filter the products and then you clicked a button which was something like 'Search for matches on Amazon' once clicked it would go off and find all the products on Amazon which were already listed matching your barcodes. You would then have to check back a little later, but it highlighted all the matched products. From here you selected them all, and added you offer details before pressing the submit button which sent them all off. It was so quick.