This is probably the best homebrew shop in Montreal. An exceedingly vast selection and a really friendly staff. Best to e-mail your recipe to them a day in advance so that they have the chance to prepare your order. While they're a wholesaler, they're happy to deal with small-scale homebrewers and have great advice on substitutions during times of hop shortages (e.g. Amarillo, Citra, and Simcoe... plus

It's far but it's worth the trip. They supply breweries in the region and also have a front desk for homebrewers that want smaller quantities.
Good selection of malts and yeast. Only down side is they don't really hold "new" hops. You'll find your classics though.
When you get there though, you have to know what you want. It's not really a shop where you can browse around. It's a counter... plus

First off, this place is a b@!%h to get to. It’s way out in the eastern part of the island, far from any other Beer-related attractions, or any other attraction for that matter, so you can’t tell yourself “I can stop here on my way to X”. It’s on the west-bound service road of the Met (highway 40), so traffic to and from here is c@!%!y regardless of time of day. Speaking of which, this place... plus