Southern Exposure Seed Exchange: https://www.southernexposure.com/
Seed Savers Exchange https://www.seedsavers.org/
Open Source Seed Initiative partners with multiple seed exchanges: https://osseeds.org/
It's actually fascinating - I remember my grandmother scooping out the seeds out of vegetables and drying them, to be used next year.
The villagers also traded them as apparently they had different varieties.
Southern Exposure Seed Exchange: https://www.southernexposure.com/
Seed Savers Exchange https://www.seedsavers.org/
Open Source Seed Initiative partners with multiple seed exchanges: https://osseeds.org/