Several for the Portsmouth to Orqunquit area that you may wanna try.and definitely more in the roadfood vein than hautecuisine..although there are several of the latter especiially near perkins cove.
Bob's in Kittery, across from the outlets have great fried clams with bellies. Also Lobster Rolls that are divine. Captain Simeon also in Kittery has all that and more in a wonderful water/river side setting. I prefer this.
For the Ultimate Lobster Experience...Chaunceys Creek Lobster. I cant descroibe how to get there, but you'll love it. Creekside and some folks come by boat. Your basic outdoor picnic tables and you can view the lobster tanks that your dinner will be taken from shortly after you order. Folks that are local make a bigdeal over this place, bringing their own table linen, wine, appetizers and desserts, etc. Part of the fun is watching them set up.and maybe stealing a bite! Chauncey's serves lobster.lobster and LOBSTER.with a few other things and a few soft drinks. You want anything else, Bring it! They don't care. Note..long walk down a wooden ramp to the docks.....not really suitable for wheelchairs or folks that have a lot of trouble walking.....and keep an eye on the kids..........they are liable to go for a dunk, but it's all part of the fun.
For the ultimate in Hotdogs.......Flo's just a little shack(actually part of a house) on Rte 1, just north of York in the Cape Neddick area. Just tell em how many you want.they'll come with the sauce! Flo I think has finally gone to the big buffet, but her daughters were running it at last visit.
Back down on the water at Cape Neddick, if it is still there, the Cape Neddick Inn on the inlet side is a good, slightly upscale place.
In York Beach, Parra's Pizza is the place locals go as well as visitors, for good reason,. Couple that with a visit to Brown's Ice Cream on Nubble Light for a fun definitely laid-back night