Amazon is a great source for a lot of gluten free products. When I buy breads, I order direct from Udi's online. They are both wonderful businesses to deal with. I totally love Udi's, but recently I found a wonderful copycat recipe that I use to bake my own! Whole Foods or nearly any health food store can be a great source of flours and grains, and so can Asian food stores, for rice and corn flours. I tend to buy only gluten certified grains and flours, because of the threat of cross contamination. Bob's Red Mill, as Joyce said, is a great source too. I only buy their oats and cornmeal, because I trust them, and have never had a problem with any of their products.