The one I go to usually is in Salem NH (just up route 93 from Boston across the MA-NH border) - Pine Tree Quilt Shop. It's a nice spot.
pinetreequiltshop.com
I've only been two two others - one small on in Chelmsford MA, Candlelight Quilts, and a very attractive one in Shelburne Falls - a lovely part of the state but a bit off the beaten path. It's called A Notion to Quilt anotiontoquilt.com and it has a long-arm machine right there in the back room. (Being a newbie I had never seen one before - what an apparatus! Like a giant table saw but more)
Sorry, can't help you with any right in the city of Boston.
Hope you get some good weather while you're here and have lots of fun
Sue