toronto to algonquin park.

This is not the fastest route. It does try provide campgrounds at potential day of cycling distance intervals while providing roads that are reasonable to extremly car free, while trying to stick to a fairly direct path. All the options have not been explored(I hear the bike trail from uxbridge might be possible if your tires are fat). There are a few spots where it looks like there may be a more suitable road. This is just more or less what I believe can work primarily based on 1 experience.

http://maps.google.ca/maps?f=d&saddr=Alden+Rd&daddr=Warden...

B is marked because it represents the last place you will find a restraunt on this route till you get to D. There are actually a few pleasent choices to be had here.
I didn't stop at C but it seems like it mike be a candidate for passing the night.
Lots of campgrounds around gravenhurst/bracebridge so that shouldn't really be a problem.

I considered doing some back-country type camping. I found this route is almost constantly surrounded by private property, though I bet with a bit of knowledge or exploration you might be able to find something suitable.
Some areas that might have some potential for setting up a tent:
-There is some trails around coopers falls(totally unsuitable for anyone but serious mountain bikers. I found it hard to even tell where trail went while walking) surrounded by forest.
-Between coopers falls and gravenhurst there were some rather sparsely poulated / no-sign of human life areas.
-Just outside of bracebridge I went on a trail ( that was not impossible for my road bike till I ran into all the sand and mud and bears). It could easily imagine passing a quiet night here. But while it was clearly marked at the begining I eventually lost track of the trail 30 minutes in(possibly bewildered by makeshift atv trails) and had to follow some power lines so as to return to civilazation without backtracking all the way.

in terms of traffic:
Obviously it could be better while your passing the heavily populated areas just outside of the city. But wasn't horrible.
Once you pass B you enter into farm land and things start to quiet down dramatically. There are still cars and trucks the pass by with some frequency.

Originally I took the 48 through talbot over to the 6. I may have made some differance that it was the friday before a long weekend. It was very busy high speed traffic. Going back I took the route mapped on a late monday evening and the traffic was very light.

After sebright (There is a general food store here...you can load up on butter tarts and cheese like I did...or other general food type fair.) all the way to huntsville seeing a car was something of a rare occurence and I got happily accostomed to being alone on the road(and only encountered one unchained territorial dog who didn't bite.) The exception to this of course is the areas around bracebridge and gravenhurst. Should you decide to go into gravenhurst take Jones rd. Bethune is high volume/speed with no space for your bike.

The 60 from huntsville to algonquin park starts out promising with a wide paved shoulder. This quickly disapears and you are left a narrow or at times no margin. The sunday of a long weekend it was quite busy. I was able to follow a side road rather than the main road around oxtounge rapids which was nice...even if i had to walk my bike up some short dirt road inclines.
A week later on a rainy monday the 60 was pretty light for traffic.