Liveaboard Marinas in New England
I'll agree that Constitution Marina is probably the most popular with the most amenities, but you also pay a price. This summer is $145/ft for 2006 summer slip. Last winter was $105/ft + $90/mo liveaboard fee + metered electric.
Boston Shipyard and Marina in East Boston also allows liveaboards at reasonable rates.
Shipyard Quarters would be another choice in Boston Inner Harbor.
All can be found in a quick google search.