I suggest Montréal, in the heart of downtown. Should be a 4 hour drive from southern NH & Montréal (all of Québec actually) feels very different from Boston. The accents, the French signs, the stores, etc, it will feel like a real vacation, due to all the differences. Plus Montréal is cheap, compared to Boston, because of the current exchange rates.

I've stayed at Bons Matins, about 2 blocks from Saint-Catherine St (similar to Boylston or Newbury), ½ block from a metro stop, on the line that takes you to the historical district & they serve a fantastic breakfast.