Watch Hill Passage to Block Island. Block Island is a great destination, truly out to sea, with enough to do to keep everyone happy. The biking and hiking trails are great, plenty of good restaurants, super beaches, etc. Try to stay a few days if possible.
Everyone knows Newport, but Narragansett Bay offers a vast selection of Harbors. Jamestown, East Greenwich, Wickford, Bristol (visit the Herrshoff Museum), and the Kickamuitt River, where I spent a Hurricane a few years ago. All fine cruising grounds.
Massachusetts & New Hampshire
Farther up the coast, a few of my favorites include all the Elizabeth Islands, especially Hadley Harbor, Tarpaulin Cove and Cuttyhunk (a small version of Block Island), in Buzzards Bay, Marion Harbor, and Edgartown on Martha’s Vineyard. Nantucket is not to be missed.
Also, there is Provincetown on Cape Cod, Marblehead, Cape Ann, Isle of Shoals off New Hampshire, and finally, Monhegan Island, which is as good as it gets (except for the swell and lack of moorings and impossibility of anchoring—wait for the day boats to head home and grab one of their moorings. Some young kid will row out and ask you for $20 no matter whose mooring you are on!) Still, the hiking on Monhegan is incredible. There’s a reason all those painters are out there!
Naturally, there are a few thousand places you must visit in Maine, but I would not miss Edgemoggin reach and the Wooden Boat School / Magazine / Campus (they have the greatest marine library I know of), Isle a Haut, Camden, Fox Islands Thorofare, Mt. Desert Island, and more!
If I’m heading to Maine, I will normally stop the first night in Old Saybrook or Fishers Island, depending on the tide.
The next day, I’ll make it to Cuttyhunk or Marion (stay in the outer harbor).
The third day, I end up in Provincetown late in the afternoon, take on fuel and water, and leave that evening for Maine. The following afternoon I arrive at Monhegan Island and stay or head in, depending on the forecast.