As a Canadian i try to support my local shops as often as possible and those would be CanadaComputers, PCvillage, iTXCanada (New to me but excellent service/shipping!!) and PremierComputerCanada...
I have used NCix.ca in the past but they lost me as a customer thanks to their "NEW" business practices. Take deposists, promise delivery, and customer receives NOTHING in the end. Not even a return of the deposit!
Newegg.ca has been used a couple times, but only sparingly, like if i can't find it anywhere else lol
I have used other stores too but only once so...
Edit: It made me lol to see the Americans reccomending American sites to Canadian shoppers lol