Depends on where you are staying/looking for.
Downtown Boston:
Near downtown crossing, where the big Macys and Filenes (and filenes basement-a MUST VISIT) are, there is Silvertone. It's a small place underground but has the best mac and cheese you will ever eat. Ever. And the prices are cheap. It's a bar with good food, how they spin it.
Near Fanuiel Hall, King Fish Hall is good. A Todd English place-his stuff is usually great. (of note are olives in charlestown as well)
For italian, nothing beats the North End. I like going to a place that is off Hanover St. (the main tourist drag). It's called La Summa Restaraunte (spelling!) and it's FAB and good value. (there are cheaper there.....Mother Anna's is divine as well and less $$ but i highly reccomend La Suma)
And, although it is a chain, you can't beat legal seafoods. (there are a few in Boston). Their Clam Chowder is DIVINE!!!!!
For Indian, Saffron on Newbury Street is great. There is also a place across the street that is nice as well (and i can't remember the name!)
Brookline: Jae's on Beacon Street (there are also ones in the city) are great. Asian fusion food, but you can get a teryaki steak there that is killer.
For a chill puby ish (ok not really-it's a sports bar but the food ROCKS) go to the Coolidge Corner Clubhouse on Harvard St.
For amazing sushi go to Fugakyu. Some serious stuff and SO WORTH THE $$$$$.
And, i have to give a shout out to Anna's Taqueria for a cheap killer burrito. In brookline and Cambridge.
I could go on all morning about this, but i have to work!!!!!
