If you use excel and USA, you can go to http://www.stampcat.com/downloads.php?cat_id=13
and download the usa.zip file. It has descriptions and other info for US stamps up to 2006 or so. You open the zip file, then open the .imp file with Excel. It is actually in a db format that excel will recognize. There are no Scott numbers included but it is in generally chronological order so mapping is not that difficult.