I have only known a couple of free canada sites :

http://international.domesticsale.com/Canada/

http://www.redleafads.com/

Oops forgot to mention those as well :

Kijiji - Post & Search Free Local Classified Ads. (http://www.kijiji.com/) probably the biggest right now

I also found a good Canadian forum at :

Welcome to the Canadian Forum ! - Index (http://www.redleafads.com/forum)