Belchertown Coop is listed elsewhere on this forum. We recently sent Mary an order for 600#s of both hard red & white and oat groats. I'm not sure how often they order -- I think we just hit at the right time.
I once Googled for local LDS canneries. I recollect there is one out near Worcester. However, I never did call to find out accessibility for the general public. I would have called, except at about the same time, I heard/read that due to legal concerns, the Church didn't want non-members near/using the canning equipment. Again -- I don't know this info for fact.
That all being said, the online LDS store (ldscatalog.com) has VERY reasonable prices on bags, 02 absorbers and if you are interested, a limited selection of #10 cans of rice, wheat and beans. Shipping is free.
If you're at Walmart, check the canned beans section. I recently found a 2+lb can of red kidney beans (Hanover), with an exp. date of 2012, for $1.30/can. It was my find for the day and several cans went home with us that day.
-ed