These out-of-the-way eateries attract the locals and offer good food at affordable prices.
 
There are a couple of Thai places in Brighton/Brookline - Rod Dee in Coolidge Corner and Bangkok Bistro in Cleveland Circle…both fantastic and inexpensive. There's also a Turkish place called Brookline Family Restaurant in Brookline Village and right next to it, a Chinese place called Sichuan Garden . Both are excellent and inexpensive.

For breakfast and lunch, you absolutely positively cannot beat Sealey's in Brookline, right off of Rt. 9. If you want locals, you'll get them here.   This is an unknown place where you'll see the same faces every single Saturday (it's closed on Sunday). They have the best omelets and club sandwiches. 
 
Coolidge Corner has a wealth of restaurants that are loved by both locals and visitors (Coolidge Corner stop on the C line). For an excellent breakfast try Zaftigs on Harvard Ave., Brookline. The place is always packed but while you wait you can check out the great shops in the neighborhood. They also serve delicious sandwiches and salads for lunch and dinner. (Their pastrami is fantastic, and made on premises.) If you're craving Thai, Dok Bua is only a few blocks away. While they offer the tried-and-true favorites, the diverse menu invites more adventurous diners to try new dishes, like the durian dessert.
 
Another good Hole-In-The-Wall is Remington's . It's right outside the Boylston T Stop on the Green Line. Come out of the station, cross Boylston Street and go to the right about 100 yards. They have great lunches and the best French fries.
 
Jamaica Plain is full of great small restaurants including Bella Luna in Hyde Square.   In Dorchester there is a great family place in Adams Village called Blasi's Cafe and Fat Belly Deli . Great food and lots of it - family run and frequented by all the locals.
 
Cafe Porto Bello , located at 672 E. Broadway in South Boston, is a tiny restaurant with only about 10 tables but they have the best lobster ravioli and veal saltimbocca.   Check the daily specials as well.
 
Delux on the corner of Chandler and Clarendon in the South End is a funky little place with great food at low prices. It is only open for dinner and has a great variety of choices.   The walls are decorated with album covers, there's a shrine to Elvis, and Santa Claus lights up the graffiti covered walls in the bathroom.  
 
For a great hamburger, Mr. Bartley's Burger Cottage in Harvard Square, Cambridge, is a "hole in the wall" that makes fantastic burgers in all sorts of combinations.  

El Pelon on 92 Peterborough St in Boston has some seriously amazing Mexican food. There are lots of places in Boston you can get inexpensive Mexican food but none as tasty as this. There aren't many places to sit inside, but there are picnic benches outside during summer.

Grotto is one of Boston's hidden gems, literally. Tucked away in a small basement in historic Beacon Hill, expect to find delectable Italian fare at unbeatable prices. While perfect for intimate dinners, this is a great spot to grab lunch in between sightseeing, given its location between Government Center and the Boston Common. You won't find a better value than the $30 three course prix fixe dinner.

** Note:  The original information for this thread came from the following forum thread:

http://www.tripadvisor.com/ShowTopic-...