if you don't mind shopping off-season, and especially if you have any interest in stuff for runners, city sports' basement on bromfield st in downtown boston sometimes has really good deals. it's just one of those places where if you go once, you might not find anything, but if you go 3 times, you might find what would amount to a few hundred dollars at full price on clearance for 40 or 50 bucks at most. i have a closet full of winter gear that i got there at probably a fifth of retail, and a plain descente jersey that was about $10.
city sports on boylston does not have a basement, unfortunately.