Building off what Sylar mentioned, try one of Montreal's walking tours. You can mingle with a group of people from around the world, get a little history of Montreal, and try food/ drinks at different restaurants around the various neighborhoods in the city. They have tours in Old Montreal, the Mile End, Little Italy, and the Latin Quarter.
I did the Brew Pub tour in the Latin Quarter last year and had a great time. While walking to the different microbreweries, the guide will give you a little perspective on the history of the area (Why is it called Latin Quarter? Hint it is not an ethnic reference.) Point out locations of old style brothels, gangster hangouts etc. We ended up at BENELUX on Sherbrooke. Had a great strawberry beer - Cricket. Our group stayed together long after the official tour ended -great conversation, good pub food, and brews. In fact I had such a good time, I barely got back to my hotel for my next appointment.
Old Montreal restaurant tour gives you a chance to sample different cuisines and maybe find a new favorite restaurant. Also you may come across a movie set because alot of Hollywood movies are filmed there. (On my tour, we came across an X-Man movie set.)
On the Golden Mile restaurant tour, we came across a free outdoor concert by a local Montreal band - the Barr Brothers.
So I highly recommend the walking tours. I have done several. and always had a great time. Great way to pass the time waiting for your next visit - learn about the history of wonderful Montreal and socialize with some interesting and adventurous people from around the world.