Don't know if these have been listed before, but at the risk of repeating I will provide details. These are both for Boston, don't know about anything outside of the city.
466 Commonwealth Ave, Unit 103
Boston, MA 02215
*This one is a true card shop, with packs, boxes, complete sets, accessories, other sports memorabilia, etc. They also deal in coins as well.
Bay State Coin Company
31 Bromfield Street
Boston, MA 02108
*This is more of a coin/currency/stamp type place, but they also keep most of the latest Topps products on hand, by the pack and box. Generally don't carry any other brands, like Panini or Upper Deck. If in need of a wax fix, it'll do, but don't go expecting a ton of variety.
PC interests right now include 2014 Bowman Chrome autos of Manuel Margot, Raimel Tapia and Austin Wilson.