These are a few places that I like to go for a bite and are not going to
cost you an arm and a leg.
Grendel's Den in Harvard Square, Cambridge is yummy, inexpensive and quite
cozy in the winter with their fireplaces! They have an international menu.
lots of variety.
Also, Chinatown is a great spot for inexpensive food as well. I love having
dim sum for lunch at China Pearl.
Ginza in Chinatown (Hudson Street) is a wonderful Japanese restaurant and I
believe they have a lunch menu that is less expensive than dinner.
Boston Shawerma (315 Huntington street) has delicious middle eastern food.
I always eat here when I go to the Museum of Fine Arts. (Yummy felafel
sandwiches) It's down the street from the museum and Northeastern University. Small
place, good food, good prices. Not fancy at all. It's like a middle eastern
sub shop.
Also, around the Copley area there is California Pizza Kitchen that has a
great lunch menu but gets crowded on the weekends. Trendy, touristy but good
food.
There is also a food court at the Prudential Center with the typical
offerings.
Hope this helps. If I think of some other places I will post them as well.