Check out this GREAT resource: The Institute for Responsible Technology's Non-GMO Shopping Guide

This list is mostly from Nourished Kitchen, full article here:

• Arrowhead Mills: GMO-free providers of baking mixes and flours found in both natural health food stores and regular supermarkets.
• Eden Foods: GMO-free providers of canned goods, noodles, tamari, miso, vinegar and Asian foodstuffs.
• Natural Choice Foods: GMO-free roviders of frozen dessert products.
• Purity Foods: GMO-free makers of spelt-based noodles, snacks and other goodies.
• Rapunzel: My all-time favorite chocolate company. They also sell speciality oils.
• Spectrum Oils: GMO-free manufacturer of speciality oils, cooking oils, salad oils and natural shortening.
• Genisoy: Uses only certified GMO-free soybeans for their many soy products.
• Earth’s Best: Baby food manufacturer uses non-GMO ingredients.
• Healthy Times: Baby food manufacturer uses non-gmo ingredients.
• Bob’s Red Mill: GMO-free provider of baking mixes and specialty flours.
• Pamela’s Products: Provider of luscious gluten-free baking mixes sources non-GMO ingredients.
• Whole Foods Store Brands: Whole foods has made the commitment to sourcing its ingredients from GMO-free sources.
• Cascadian Farms: Provider of frozen entrées, juices, frozen vegetables and fruit, yogurt and other foods.
• Imagine Foods: GMO-free provider of soy and rice milk as well as broth and other foods.
• Muir Glen: Source of canned goods and vegetable juice uses gmo-free foods.
• Thai Kitchen: Source for coconut milks and Asian ingredients sources gmo-free ingredients.
• Amy’s Kitchen: GMO-free source of canned soups, chilies, boxed and frozen meals.
• Nature’s Path: Manufacturer of cereals and snack bars made with ingredients sourced gmo-free.
• Annie’s Naturals: Manufacturer of BBQ sauce, salad dressings and other condiments sourced from gmo-free ingredients.
• San J: GMO-free manufacturer of soy sauce, shoyu and tamari.
• Tradition Miso: Manufacturer of miso pastes that are made from GMO-free ingredients.
• Barbara’s Bakery: Manufacturer of cookies sources from gmo-free ingredients.
• Lundberg Family Farms: GMO-free provider of rice and wild rice foods including raw rice, soups and convenience foods.
• Walkers: Provider of the best shortbread cookies ever as well as other sweet treats.
• Fantastic Foods: Provider of hummus, falafel, risotto couscous, soup and other mixes with gmo-free ingredients.
• Vitasoy: Manufacturer of soy-based foods sourced from gmo-free ingredients.
• Clif: Manufacturer of energy bars sourced from gmo-free foods.
• Kettle Chips: GMO-free manufacturer of potato and tortilla chips.
• Que Pasa: Manufacturer of tortilla chips and other Mexican foods sourced from non-gmo ingredients.
• Garden of Eatin: Manufacturer of chips, salsas and other snack foods.
• French Meadow Bakery: Manufacturer of bread and baked goods using non-gmo ingredients.
• White Wave: Manufacturer of soy products including tofu and tempeh using gmo-free soy.
• Bearitos: Manufacturer of snack foods and dips using gmo-free foods.
• Chaffin Family Orchards: Is committed to GMO-free foods and sells an assortment of goods including olive oil.
• Cultures for Health: All starters and products sold at Cultures for Health are GMO-free.
• Grindstone Bakery: GMO-free provider of wheat- and gluten-free bread.
• Pure Indian Foods: GMO-free provider of grass-fed ghee.
• To Your Health: Provider of gmo-free sprouted breads and sprouted flours.
• US Wellness Meats: Provider of pasture- and grass-fed meats free of GMO supplemental feed.
• Zukay: Provider of live cultured condiments and salsa free from GMO.