Although Crescent is a good spot to head to, you might want to venture to St.Laurent street instead - I personally prefer the ambiance offered by the clubs away from Crescent. For the most part I find Crescent to be WAY too young (except Thursdays). However, it all depends on the kind of music you like, the crowd you prefer, etc...
Here are some of my favorite spots where you just might run into me:
Juice Nightclub -
More house mixes than anything
Orchid Nightlounge - G-Spot Fridays rule!! - here is the flier for that weekly event
http://images.clubzone.com/events/images/12298/12298.jpg
The 1234 nightclub on de la Montagne is quite nice too (the address is 1234 de la Montagne
Another new place (well, technically new, but used to Blu) is the Roxy - where a good friend of mine DJs on Friday nights... it is located on Stanley, above Ste.Catherine.
I also like Thursdays and occasionally hop into my young vibe and run into Sir Winstons, I am not saying that the clubs on St-Laurent are much older, but Crescent street tends to attract the newly qualified to drink crowd, whereas St.Laurent is a bit more, hmmm, sophisticated - sometimes in the bad way, where you cannot get into a club because you don't know the DJ (I am lucky enough to know most of them!)
Montreal is a great place to party, regardless of the season, so you cannot go wrong... have a great time here
Melanie