Welcome to Scubaboard!
There are plenty of dive opportunities up here including both shore diving and boat diving.
If you need to rent gear, there are a few shops in the Boston area that have rental equipment available. Two that I recommend are Boston SCUBA (full disclosure, I'm a part time captain on their boat) and East Coast Divers. East Coast Divers is located in Brookline and Boston Scuba is located in the East Boston Shipyard and Marina. Boston Scuba has the benefit of having an onsite dive boat that runs Thursday through Sunday during the summer and Saturday and Sunday year round. They don't do much shore diving, so if you're looking to shore dive, I'd recommend posting here for a buddy or on Facebook (New England Scuba Divers group). If you're looking for a guided shore dive, East Coast Divers has an active schedule of shore dives during the year.
For shore diving, I'd recommend picking up A Shore Diving Guide to New England by Jerry Shine. This is an awesome reference to most shore sites in the area and is available at most dive shops.
Like I mentioned before, I recommend joining the New England Scuba Divers group on facebook as that is a great resource for meeting a buddy and getting introduced to the local area.
If you want to go on charters outside of Boston, there really aren't any that aren't top notch. Aside from Boston Scuba, Cape Ann Charters (the Daybreaker) and the Gauntlet (more tech and advanced orientated) are my two go to charters. Cape Ann Divers also runs a great operation and I'm usually out with them a few times a year as well.
Feel free to ask around if you have any questions or shoot me a PM