After or as part of drysuit, I HIGHLY RECOMMEND DRYSUIT, even in the summer especially if you to go deep.
Other certs depend on what you want to do. Lots of shore diving in cape ann and Rhode island. There are a lot of wrecks from 15 feet to need trimix and a rebreather to do and reefs you can get to from boats if you want to go that route ask the operators about there requirements they might want deep and or advanced for them.
The recreational ones I know of are Boston Scuba in boston, giant stride in Warwick RI, new England dive center which runs it boat out of stoneington CT and the cape ann II out of cape ann MA. I know one other boat but I'm not sure if they do rec dives.