On River St, there is Great Eastern Trading Co. (vintage, mostly women's). Further down (away from the Square, towards the river) and across the street is a men's clothing vintage / used place (Keezer's?).  Back to Central Square, there's a Goodwill store. There used to be and MIGHT still be a store with exotic clothing and lingerie and paraphernalia not too far from CheapO records and the Middle East Restaurant. ALL of those are walking distance from the Red Line subway stop.  
.
Head up Mass Ave, towards Harvard Square for Oona's vintage clothing.