We are gardening for the first time really, so I don't know about your area because we live in Florida but some nice people here at gardenweb have given us names of some seed co. they think are good to order from. The companies recommended to us are: Sandhill Preservation Center, Victory seeds, Baker Creek (rareseeds.com),Seed savers Exchange, Mariseeds.com. I can say that I have ordered twice from Dianeseeds.com (Diane's flower seeds) & got heirloom veggies for good prices, quick service too. We are growing lettuces, tomatoes & eggplants mainly but are hoping to add melons, beans, cukes soon. Diane is very nice & includes a freebie pkt of seeds with every order & so does baker creek heirloom seeds (rareseeds.com)
Oh, also for tomato seeds you can try wintersown.org for open pollinated tomato seeds, several varieties. Trudi (she runs it) is nice. She will send you (you choose from a list she posts on her site), 6 varieties of tomatoes when you send her a two-stamped sase. She will send you your choices in small sample sized pkts. Also she throws in some other seeds too, she gave me flowers, lettuce & peppers & beans. On her site, go to the free seeds/gateway to the seeds section for the current list of choices. :) Her tomato seeds are now also growing nicely in our little garden along with some from Diane's flower seeds.
Good luck & happy gardening.