I used to live in Watertown, and my favourite LBS was Belmont Wheelworks. Well worth a visit or three. Be warned, I am a sucker for gorgeous lugged steel frames, and ended up with two of Peter Mooney's from Wheelworks. Harris is also fun, not nearly as large as Belmont Wheelworks, but if you are a utility cyclist, they are a goldmine. Great BBQ joint just down the street too .