I'm on the mailing list for all the major seeds suppliers. Today I sat down and compared their shipping and handling charges.
If you only need a few packets of seeds, and you're not wedded to any particular variety, you may be able to buy from any company. You may want to choose to buy from a company that keeps their shipping (and/or handling) charges low.
Bountiful Gardens has the least expensive charge. Bountiful offers heirloom untreated, open-pollinated seeds from their Ecology Action operation in California. Bountiful has signed the safe seed pledge meaning they do not knowingly sell GMO seeds.
Bountiful offers a great number of outstanding varieities, including some of my recommended varieties:Winter Density lettuce, Chioggia beets, Jimmy Nardello peppers, Sugar Snap peas, and Glacier and Pruden's Purple Tomatoes They also have the Cocozelle zuchinni which I intend to try. It is one that is very good tasting.
The runner up is Pinetree Seeds out of Maine. I love looking at the Pinetree catelogue for the wide variety of seeds and accessories. They have several of my recommended varieties including the Sun Sugar cherry tomatoes, Diva cucumbers, Mokum carrots and Cheddar cauliflower.