While the above links are a great for Niagara Falls it sounds like you are venturing a bit further north.
If you do choose to stop in Niagara Falls another good resource is,
www.gterb.ca.
For the Toronto area,
www.terb.cc.
Montreal,
www.merb.cc
If you are looking to avoid a bad time stick to the well known agencies and stay away from Leolist and Listcrawler. While there are some great indi's up there the women working at the agencies are amazing. Save yourself the time and hassle and just stick to them. Not going to compare to down here because there isn't a comparison.
Have fun and stay safe!