definitely have dinner at L'Express (3927 rue Saint-Denis) if you have a chance...it's on the pricey side, but you won't be disappointed. what isn't pricey in montreal anyway?
there's a great sneaker shop down in old montreal...can't remember the name, but lots of famous musicians and artists stop by and sign the walls when they're in town. plus, amon tobin works at the shop next door to it.
schwartz' deli has the best smoked meat sandwiches...worth a wait in the line outside, even in cold weather.
if the weather is nice, a climb up mont royal is a good diversion with excellent views of the city.
bar bily kun is nice and there's a great lounge around the corner that has live dj's spinning 60's garage rock and other good stuff. both are a short walk up the street from L'Express.
have fun!