You could also make a nice loop based out of Boston or New York, doing the same states Catamount mentioned. Of course Marcy and Karahdin will take some time, and you have to decide whether to drive or climb Washington (I'd say definitely to hike it), Mansfield (where a road goes almost to the top), and the one in Mass (I forget the name). I'd recommend hiking all of them. New Jersey's highpoint is also paved to the top, but its not as much of a mountain as the others.
In the space of about a week you can comfortably climb all the NE highpoints, as long as the weather is okay.