Top 5 (in no particular order and why:
1. Cathedral Rock - shore
The sttep dropoff at these rocks means you can get to deep clear water fast... a few hundred feet from shore, and you can be at 75'. I've also seen huge schools of fish every time I've been there.
2. Minot Light - boat
A great range of depths from 5' to 50', and the vis is usually excellent. Tons of fish, including stripers, dogfish, cod, etc... and the biggest flounder I ever speared. It fed four of us. The remains of the old scaffold lighthouse are still there, as well as debris from the many ships that have wrecked on the ledge. It looks like a good spot for lobstering too, but I haven't fully explored that option yet for want of a boat. Definately my favorite site so far, and one I grew up with... it's right off my home town, and relatives helped design and build the new stone lighthouse.
It can be tricky to approach though. I recommend taking a Zodiac launch from a larger boat.
3. Idene - boat
Very nice, for all the reasons described in previous posts.
4. Chester Polling - boat
It's a cool half wreck, and the first deep New England dive I ever did. I find that it continues to be a good skill-building dive for me, and I hope one day to break "the curse" and get a good night dive in on her.
5. Ft. Wetherill - shore
I saw a spotted butterfly fish here... in Rhode Island. 'Nuff said.