Off Grid Info has put together a giant list of heirloom seed companies.
Keep this list handy as there will be a time when seeds are sold out in the stores.
30 Survival Heirloom Seeds – Save your own seeds – Here
Storing Seed Tips – 84 Pages Of Storing Seeds and more – Here
How to store tomato seeds from your crop
Use Silica Gel to save your seeds, along with a food saver vacuum sealer – find it here.