Besides Value Village and Renaissance, what stores do you go to, and for what type of goods? I mostly look for physical media, and electronics that I consider valuable.
I haven't found too many other stores yet in Montréal, but there's Friperie Notre-Dame in Lachine. They have decent physical media.
On the other hand there was the Habitat for Humanity Re-store, the one in St-Henri. They sold books and some records. It just went out of business and I can certainly see one reason why: selling donated or trash-picked furniture for as much as twice the price of a new item. Crazy.
I think they got upset at me one day because I saw a 9" Sony Trinitron in perfect condition with no price tag and the cashier just said "five bucks" and I barely had the time to slap a fiver on the counter when the manager came running at Mach 2 but too late.