Another New Englander? Woot!Any suggestions?
New-Englander-in-exile, and lived in Cambridge for a few years.
LA Burdick (i.e. "Burdicks") has legendarily good hot chocolate.
There's a Peets Coffee/Tea in the square, as well as a Ben and Jerry's and a Starbucks in The Garage. Not much seating or ambiance in the Garage, though.
Farther away from Harvard Square (about halfway between Central and Kendall), there's Toscanini's-- ice cream and coffee and such. And Cafe Luna-- the same, but with (at least, the last time I was there...)
gelato frappes.
And there's also 1369 Coffeehouse on the Harvard side of Central Square proper.
For slightly more substantial food (and greasy, too!) there's Bartley's burgers on the Central-square-facing side of Harvard Square, and Crazy Dough's pizza in the Garage. Border Cafe isn't really worth it-- New England-style "Mexican" food.
There are lots of other restaurants up and down Mass Ave., but these are the places that I've actually been to.
Bring up Google Maps centered on Harvard Square and I'm sure that you'll find someplace you want to go.