Just looking through the comments since earlier, many of the places I would recommend have been mentioned. If you make a trip up to Burlington area for Gardener's Supply, check out City Market (the one on Flynn Ave), because they sometimes have a few different seed vendors' stuff on display.

I'd also say check out Red Wagon Plants (Hinesburg) and GreenHaven (New Haven), but I don't think either of them are open for the season yet.

Finally, I'll say that I heard this scuttlebutt on a gardening forum I'm on: Baker Creek Seeds is a right-wing company with some fundo-Christian background stuff going one beneath their (very lovely) veneer. They do have tons of weird things though, and I used to order from them a lot, but now I'm having second thoughts about it. Not sure if this matters to you or anyone else reading this, but I just wanted to share in case it does.

Happy growing!