<<Disclaimer: Verify this information before applying it to your situation.>>

Thanks to all of you who responded so quickly to my request for
information.  Here is a summary:
These products ARE gf:
Hellman's Real Mayonaise- regular & light
Heinz Vegetarian Beans
Bush's: All "Bushes Best Products"
Best original baked beans
Best vegetarian baked beans
Mazola if made with corn oil is GF

As for shopping guides to American products, I got two recommendations:
"The shopping guide I go by is really great......updates every year to the
products."
You can order it by sending $10.00 to:

TCCSSG
34638 Beechwood Street
Farmington Hills, MI 48335

"about the best for US food is the 84 page _CSA Cooperative
Gluten-Free Commercial Products Listing"_:
$8.00 from: Celiac Sprue
Association/United States of America, Inc., P.O. Box 31700, Omaha, NE
68131-0700.

Finally, for my fellow Israeli list members who may not be aware, guar
gum (though as far as I know not xanthan gum) is available in Israel.
Ask your pharmacy to order Guarem made by Orion Pharmaceuticals,
imported by Lapidot Pharmaceuticals in Herzlia Pituach.  It comes in a
box of 30 sachets, 5 grams each for 60 shekels.