My husband and I are contemplating a trip to New England late in September. Can you give us some direction about where to go to get the most out of a week? We love to see quaint towns, beautiful countryside, interesting architecture. Where is a good starting/stopping place?

Do a search on Fall Foliage for each of the New England states, or at least NH and VT, here on this forum. You will be just ahead of the foliage season but you should still reserve as soon as possible. If you're flying, choose either Manchester NH or Providence RI. You might head to Stowe VT and enjoy northern VT or stay in central VT, maybe Middlebury. Woodstock VT is one of the prettiest towns.
In NH the best city is probably Portsmouth NH. The buildings are beautiful and then there's Strawbery Banke. You might split the week between the coast and the mountains. Meredith NH on Lake Winnipesaukee is a busy town with some great hotels but for quiet drive thru the Sandwich/Tamworth area. On the day you switch locations, stop in Canterbury NH for a tour of Shaker Village.
In CT I was surprised at how much I liked the Mystic CT area but we lucked into a wild mushroom festival at a lovely little nearby nature museum in late September last year. Abbotts was still open for lobster rolls. The Indian Museum at Foxwoods was fascinating but again, I would spend a few days in that area and then explore Rhode Island. The weather should be wonderful.
It would be possible to split the week between Portsmouth and Stowe. It would be a long drive but a great one. Explore antique shops along Rt 4 in Northwood, late lunch in Woodstock VT. But if you like organic food and high quality handmade crafts, I would head to Camden Maine and attend the Common Ground Fair.
Have fun deciding!

dfrost, as usual has given you some great advice, especially about booking your lodging early. Weekdays should be no problem if you want to "wing it", but definately reserve lodging for the weekend to play it safe.
If you want to see some fall color, you'll want to stick to very northern New England and Southern Quebec in late September. Manchester NH is a good airport to fly into, but also look into Burlington, VT or even Montreal. Many folks who come to Vermont just love Stowe. Stowe makes a good base for touring Northern Vermont and has many choices for lodging and restaurants.
Also consider a night or two in the White Mountains of NH. I would recommend staying at the Mount Washington Hotel-it's just gorgeous.
Some other websites to check out:
www.scenesofvermont.com
www.gostowe.com
www.newengland.com
Have fun!

Thanks to both of you for some really great information - sounds lovely!!

We live in Southern New Hampshire and have weekended all about for many years. New England is a huge territory, and TIMING is everything.

Be advised that you should make reservations for accomodations forthwith. With airfares to Europe so high, and the exchange rates so dismal, the New England tourist offices are predicting record visitors this Fall.

I would recommend "Best Loved Driving Tours of New England" to determine those destinations you might find most appealing.

Our favorites are Stowe, Vermont; Lenox, Williamstown, or Stockbridge, MA; Franconia and Jackson, NH. But, there are also dozens of "destination" country inns all about. You can hardly go wrong.

Another wonderful resource is http://www.yankeemagazine.com/foliage/

For a one week visit, I'd recommend checking a foliage map and picking one or two states according to your dates, and depending upon how much driving you care to do - keeping in mind that the very best way to enjoy the foliage is driving all over.

Late September is a bit early, so you'd want to stick to the very most northern NH and VT, probably. The colors begin to change in the most northeast, then move south and west. "Countryside" would be splendid in Maine, but "interesting architecture and quaint towns" are far more sparse.

Note that the leaves change last near water - Lake Winnipesaukee and Portsmouth (on the coast) are usually still quite green in late September.

You may wish to consult http://www.yankeemagazine.com/foliage/findcolor.php, then plan accordingly, or adjust your dates.

Thanks djkbooks for your great advice. If all of the people in New England are as nice as you, we should have a wonderful time. By the way, do you rent out rooms? (Just kidding!)