Is there a list on the web where I can find the name of a company
making or selling a product by using the UPC number on that product?

Hi joebezzy,

Here you go -

How Do I Get A List Of All The Product Codes And Their Respective Manufacturers?
"There is now a complete, free on-line database that allows anyone to
type in a UPC or EAN number and get the company information for the
product. It is a project developed by EAN International and is called
GEPIR. You can go directly to the UPC and EAN search page by clicking
here. Please note that sometimes GEPIR is down. If you get a "page not
available", try later. Currently, the database does not return the
product description. It only returns the company name and address."
http://www.adams1.com/pub/russadam/new.html

GEPIR Search
http://www.gepir.org/client.htm

Internet UPC Database
Click on "Look Up UPC"
http://www.upcdatabase.com/

You now can purchase a UPC database from Gregg London.
http://www.glondon.com/upcdatabase.html

Additional Links of Interest

2005 Sunrise and the Global Trade Item Number ­ in English!
http://www.adams1.com/pub/russadam/2005-sunrise-gtin.pdf

Bar Code 1
http://www.adams1.com/pub/russadam/upccode.html

I hope this is what you are looking for. If not, or if you have any
questions, please post a clarification request and wait for me to
respond before closing/rating my answer.

Thank you,
hummer

I searched my own bookmarks and followed links.

Excellent and timely response.

Dear joebezzy,

Thank you for your nice note, rating, and tip - they are all
appreciated. Sincerely, hummer