Here’s the list of companies that specialize in heirlooms and organic seeds that are NOT owned by or get seeds from Monsanto or Seminis. :
This list is of seed companies/suppliers that I could validate a functional website for. I do not include companies/suppliers that only have Facebook pages with no actual website.
This list of seed suppliers is far from complete and I will add to it as I find new ones.


USA:


Adaptive Seeds
All Good Things Organic
Amishland Seeds
Annie’s Heirloom Seeds
Backyard Beans and Grains Project
Baker Creek Seed Co. (Rare Seeds)
Beauty Beyond Belief (BBB Seeds)
Botanical Interests
Bountiful Gardens
Diane’s Flower Seeds
Farm Direct Seed (Hobb’s Family Farm)
Fedco Seed Co.
Gourmet Seed
Grow Organic
Heirlooms Evermore Seeds
Heirloom Solutions
High Mowing Seeds
Hudson Valley Seed Library
Growing Crazy Acres
Ed Hume Seeds
Irish-Eyes
J.L Hudson
Kitchen Garden Seeds
Knapp’s Fresh Vegies
Lake Valley Seeds
Landreth Seeds
Larner Seeds
The Living Seed Company
Livingston Seeds
Local Harvest
Mountain Rose Herbs
My Patriot Supply
Native Seeds (for the Arid Southwest)
Natural Gardening Company
New Hope Seed Company
Nichol’s Garden Nursery
Organic Sanctuary
Prairie Road Garden
Renee’s Garden
Restoration Seeds
Sand Hill Preservation Center
Sage Thymes
Seed for Security
Seeds Trust
Select Seeds
Siskiyou Seeds
Southern Exposure
Sow True Seed
Sustainable Seed Co
Tomato Fest
Trees of Antiquity
Turtle Tree Seed
Underwood Garden Seeds
Uprising Seeds
Victory Seeds
Vermont Wildflower Farm
White Harvest Seed
Wild Garden Seeds
Wildseed Farms
Wood Prairie Farm


Canada:

Annapolis Valley Heritage Seed Company
Brother Nature
Cubit’s Organics
Full Circle Seeds
Greta’s Organic Garden
Heritage Harvest Seeds (ships to Canada only)
Hope Seeds
Incredible Seeds
Richters Herbs
Salt Spring Seeds
Solana Seeds
Stellar Seeds
Terra Edibles
The Cottage Gardener


Europe:

Garden Organic (UK)
Seed Site
The Real Seed Catalogue (UK)