I'm not sure where in Boston you are but there are a ton of farmers markets. best place to find the closest one to you would be
http://www.mass.gov/agr/massgrown/
I know of a few of the top of my head there is one in city hall plaza, back bay across from the public library, I know there is one in JP, Milton has one in lower mills, Quincy has one near the public library, Roslindale has on in the square, there are 2 in Dorchester one is run in collaboration with a local farm, Brookline has one honestly I think the best ones are in town and the one in Quincy they have a much larger selection and more vendors The one in Milton is nice too.
2 local CSA are from
http://www.allandalefarm.com/csa/csa.html
and
http://thefoodproject.org/csa.
I've done the food project winter csa and loved it.
You can also sign up for a local seafood share through
http://www.capeannfreshcatch.org/
You can sign up for meat shares through (I'm sure there are others but I'm not really familiar with them. Though I know you can also buy meat through the food projects farm in Lincoln ma. The selection is slim and is all frozen)
http://www.thebutchershopboston.com/#retail
Also chicken and pork from (but good luck getting a chicken unless its an extra since they always seem to sell out early in the season)
http://peteandjensbackyardbirds.com/
If your looking for something more specific send me a pm I go to a few of the local farmers markets and get a local csa. I've been trying to keep everything as natural as possible while staying on budget (kinda lol)
I love Wilsons in lexington also.
I hope this list helps.