Victor:
Adirondacks of NY, Green Mountains of VT, White Mountains of NH, are all great places to be traveling in the summer. I did those routes every summer for about 15 years, going from Ottawa to Maine, in late July, early August.
If you are leaving from Toronto, I assume you'll cross into NY at Thousand Islands. I believe its Hwy.3 that takes you from near Watertown to Saranac Lake and Lake Placid. At that point, your first big decision is whether you'll take a ferry across Lake Champlain, or drive around the top or the bottom.
Once in Vermont, I recommend that you stay off the Interstate (unless you really need to cover ground quickly) and follow the secondary roads through the mountain passes and valleys. The scenery is fabulous and you'll have more fun going through all the little towns. Lots of mountain streams and small rivers where you can toss your canoe in and enjoy paddling about (although that's one thing I never really got to do on my travels). Saw lots of others doing it. Same story holds true for New Hampshire. Two of my all-time favorite places to travel. Just don't be anywhere near southern NH during a NASCAR race weekend at Louden. Every motel within 200 miles will be booked solid. (I once drove almost the whole way back to the Quebec border looking for a room, then wound up sleeping in the car).
Doesn't really matter which of the back roads you take through the hills; they all have great little places, lots of antique shops, things to do and see. I tried to take a different path each year, so I've been on most of the roads and through most of the passes. I have a couple of favorites, but they're all fun.
Enjoy yourself. I'm envious at the thought, and reveling in my memories.
power boats. The Fulton chain of lakes is also a nice paddle in the area.
