It may be presumptuous of me to assume the general public understands the definition and the difference between heirloom seed or a non-GMO seed. I think it is important to clarify the difference. Heirloom seed, for example an heirloom tomato can be defined by Wikipedia as an heirloom tomato (also called heritage tomato in the UK) is an heirloom plant, an open-pollinated (non-hybrid) cultivator of tomato. Non-GMO seed (non-genetically engineered seed) is seed that has not been altered genetically. For example corn that is designed to resists pests. I think blogger Annie B. Bond has a great article called Why it matters to buy heirloom discussing both.
If you are interested in purchasing heirloom seeds, I found a great list of companies that sell heirloom seed. Check out the list on the Southern Organic Resource Guides web site. I feel it is important to grow heirloom because I find a huge difference in the taste and look of heirloom varieties. I also find it quite frightening to think that maybe one day we will not have the variety of fruit, flowers and vegetables as we do today, due to seed extinction. It is great that groups like the seed savers exchange have supported the efforts to save the seeds from our yesteryear. Below is a passage taken from Seed Savers Exchange website which nicely sums up there goals:
Seed Savers Exchange exists to serve its members, and the public, through its charitable mission to (1) save the world’s diverse, but endangered, garden heritage for future generations; (2) build a network of people committed to collecting, conserving and sharing heirloom seeds and plants; and (3) educate people about the value of genetic and cultural diversity