Ma petite pêche fraiche:
Once you leave the sport climbers' mecca of the Bruce Peninsula, and get on the ferry to Manitoulan Island, you are leaving the most developed rock climbing areas in Ontario. While in the south, be alert to access issues and permit systems for provincial park lands. MEC Toronto has the guidebooks you will need.
Above Lakes Huron and Superior, there are dramatic cliffs, but it is mainly volcanic/basalt-like stuff, tremendous for ice climbing but less so for rock; that which is more solid is not very well developed. I would go canoeing, instead! It is glorious country.
As you may know, Shaun Parent is the wise old man of this area of Canada. Drop him a line at North of Superior Climbing Company, above The Soo.
http://www.northofsuperiorclimbing.com
Consider climbing at Montreal River Harbour, an hour above the Soo, as it is probably the best developed area in central Ontario. Parent published a guidebook for Ranwick Rock and Keetes Bluff a couple of years ago. I haven't climbed there.
At Thunder Bay, there is Scenic Bluffs, Climbers Cliffs, Pass Lake, Silver Harbor, Squaw Bay, Mt. Helen, and Kama Bay. See, "Thunder Bay Rock Climbing Guide", Alex Joseph, 2003. There are a good number of climbers in this area, especially out of Lakehead University's "Outdoor Recreation" degree program, so the routes should be in better condition. I haven't climbed there since 1999, and that was at Lake Helen, above Nipigon.
There used to be a climbing gym in Thunder Bay, but I don't know its status at present. Might be a source of ideas.
Enjoy the Great White North, Eh? If there was a God, this would be his country. Mind the bugs, though ...