How are regular Sunday drives starting around 8am from Manhanttan to Toronto compared to this Sunday (Nov 29th '04) with the Black Friday rush? Is there another time to leave which will be a shorter drive? How long will the border crossing take? Does the Black Friday thing even last till Sunday? Is there a particular train line that is faster?
It's a holiday shopping weekend, so you should expect traffic in any city concentrated around shopping areas such as malls, as well as heavier traffic on arterial roads. And Manhattan of course will be Manhattan, but you won't be there long.
If you just follow Google Maps it will advise you to take the Holland Tunnel out of the city, which ought to be light traffic at that time of the week, and direct you onto I-80 west. This gets you out of the urban areas very quickly.
Later you will cross into Canada at the Lewiston-Queenston Bridge, downstream of Niagara Falls, which will not have quite as much tourist traffic as the Rainbow Bridge crossing. Expect your wait to not be all that long there; historical wait times for the Sunday night after Thanksgiving are around 45 minutes at peak hour (6 pm to 7 pm), but you should arrive a couple of hours ahead of this. And remember to bring cash for the toll.
The remainder of the trip is rural freeway and you should not see any significant traffic, barring accidents, which is quite possible if there is more snowfall (though most of the roads are clear right now). It seems some snowfall is predicted for the Syracuse area so you might want to take Google's alternate suggested route to bypass most of it. That route uses the Peace Bridge though. You may want to check live wait times when you get to Buffalo to decide where you want to cross.
So, call it about eight hours, plus border wait, plus however long you stop for food, gas and other necessities. Assuming an hour for food and gas, 45 minutes at the border, and 15 minutes to get out of Manhattan, a ten hour trip.