Local beers w/ cranberry?
Not all that local but, Unibroue Ephemere Cranberry is pretty tasty - at least the last time I had it at Redbones (must have been a couple of years ago now) - you may find it in bottles at the better beer stores around town.
Rock Bottom (Boston) made a cranberry ale last spring.
Buzzard's Bay made a cranberry lambic last year - may still be bottles left at the brewery?
Other places (Portsmouth brewery, Cape Cod Brewing) have made cranberry flavored beers in the past, but not on a regular basis.
Whether Sam Adams is a local brewer might be up for debate (since most beers are brewed out of state) but they make a cranberry lambic that is available in their winter mix pack (and at one point in a 22oz bottle). The mix pack probably won't be out for a couple of months (maybe a little less) so it is not going to be available if your looking for something right now.