Any places along the Merritt Pkwy (CT)
For family reasons we will be traveling a lot between Washington and Boston - on the way we can usually avoid the dreck on the NJ turnpike with a picnic, but last time we got to CT and were starved ( and you know a traffic jam plus hunger = bad trip).
Any places close to the Merritt, our preferred route, or along i91 before Hartford?
It's a pretty broad topic that you have chosen, and as @stamfoodie noted, the Parkway deliberately skirts most commercial areas. I'm assuming that you are looking for worthwhile, interesting, quick stops while driving, rather than fine dining.
Near my home area, there are commercial strips off exits 35 and 40. Both have various fast food options, but my suggestions include Layla's Falafel and Ole Mole (Mexican), and Fratelli Ravioli (for heroes) just south of exit 35. None is fine dining, but all are quick and tasty. Just north of exit 40 is Brasitas, which is a full service restaurant with a solid Pan-Latin menu.
When we travel north on the Merritt, we often stop for steamed cheeseburgers at Ted's Restaurant in Middletown (where the Merritt meets 91). They sound weird, but they're a regional specialty and my kids love them. On a recent trip to Hartford, we discovered a branch of Nardelli's grinders just off exit 21 on I-91. We often stop at one of the mini-chain's branches when we travel up Rte 8 to I-84 (which is a route that can avoid some potentially horrible Merritt traffic on Friday nights or during construction). They make a variety of good hot and cold sandwiches that are popular with the whole family.
(btw, I just made a mental note to try Ernie's in NH on a future ride on @bagelman's rec)
If you can answer some basic questions I'll try to make some suggestions.
Day of week? Time of Day?
Some places are closed Mondays or don't serve lunch
Type of Food?
Full Meals, burgers/dogs/fried seafood, Apizza, Chinese?
and I assume by the Merritt, you also mean the Wilbur Cross from the Milford line to Wallingford..........................
That said, for very good New Haven Apizza without going all the way into town:
Ernie's Apizza 1279 Whalley Ave New Haven 203-387-3362. About 3-4 minutes from exit 59 going towards New Haven.
NOTE: This is for Pizza only, no subs, no pasta.
4.5 stars (I am a Sally's Fan, but this is worth eating for more than 40- years).
Glenwood Drive In north of Exit 61 in Hamden on Whitney Ave. Great dogs/burgers.fried seafood and onion rings. NO AMBIENCE, self serve, plastic tight booths.
Upscale, but delicious: Mickey's 2323 Whitney Ave Hamden, again north of exit 61, but only about 1/2-3/4 mile. Wonderful continental food with a middle eastern twist, great bar and wine list. Lunch and Dinner
The Hamden Town House, right off the Merritt exit 61/62, is a good diner. Excellent breakfast all day & night, good homemade soup-of-the-day, pretty decent basic sandwiches, burgers, daily specials, etc. It's plain food, nothing fancy, but I generally enjoy what I eat there. (The building used to be a HoJo, so it doesn't look very "diner.")
I also agree with Clams047, the Glenwood Drive-In has great hot dogs & fried seafood. They also share a roof with Kelly's Kone Konnection, really good homemade ice cream.
There's another diner right off exit 60 (the Acropolis) - a little plainer on the plain-food scale, but I like their moussaka better than the Town House. Also at exit 60: There's a bunch of fast food & fast casual chains on Dixwell Ave north of the Merritt overpass there, and Ibiza Tapas (very good tapas) a block or two further south.
You did not indicate a preference, but for a basic hotdog, lobster rolls or just some of the best fried clams this side of Maine, I highly recommend Glenwood Drive In at exit 61/62 off the Wilbur Cross in Hamden for an easy on/off and quick service.
Another stopping point for us is the Cromwell Diner at exit 21 off I-91. It's more like a Jersey diner than typical New England diner - nice selection with very good quality. From what I recall, they serve breakfast all day and are open quite late (11pm and 24 hrs on Fri/Sat).
Slim pickins' because Merrit built to bypass urban commerical areas.
Try Barecelona at the HiHo Motel off Exit 44, Blackrock Tnp. in Fairfield. Sensational small plates and tapas, consistently winner of tapas awards. Don't be put off by the appearance of the Motel.
For breakfast, Lakeside Diner at exit 34, Long Ridge Road, Stamford. Best pancakes in the state and yummy cinnamon donuts, still warm. Avoid everything else, especially the coffee.