Steve Kotalac from Nantucket Tackle Center reported that bluefish are everywhere around the island; from shore, he suggested Tom Nevers and Dionis as two areas to try your luck using topwater plugs. Sankaty and Old Man Shoal have a mix of bass and bluefish and they are being caught both casting topwater plugs or soft plastics (for bass, of course) or jigging wire.
When it comes to big bluefish, Nantucket is as good a bet as your will find around the Cape and islands, with double digit fish not unusual. The harbor has a good number of stripers and folks on the island find soft plastics a very effective way to catch them. As Steve said, a couple of years back he had about a one foot section of soft plastics and now he has an entire wall.