Vineyard Haven on Marthas Vineyard works similar to Northport. They have a short stay town dock where you can wash the boat and fill tanks. The moorings are expensive and dock space is astronomical. But the anchorage is good in the prevailing southerly winds. With a north wind...ouch! And ferry wakes do keep you rolling during the day.
The Stop n Shop is right in town, about 4 to 6 blocks from the dink dock. There are banks, drugs, hardware, etc. Don't recall laundry. Considering it's in megabucks New England, its a good stop.