What kind of yarn are you looking for?
I have ordered from http://www.herrschners.ca/
and their discount store http://yarnsale.herrschners.ca/
I believe they actually have a store front in Kitchener. They can be very reasonable especially when they have yarn on sale! They can take awhile to arrive though.
I also just bought some great cotton from:http://www.camillavalleyfarm.com/
I bought their worsted weight, but it's a not as thick as the worsted I need. A bit thinner. Gorgeous colours though.
Good luck. I hope this helps.