If you're going to Toronto try TD Canada Trust (the Green banks) or this place on Carlton Street. hell, he even has ARS last time I went there:
http://www.collegecurrency.ca/
He's at 25 Carlton Street (less than a block East of Yonge and Carlton/College, subway station right there) You'll get a bit better than the bank
rate.
Remember, the best rate is if you have a Debit card from Bank of America. You can use it for free at Scotiabank (cherry red colored banks)
for free.
As others have said, places will take USD at par basically, rate is about 1.07 CAD to USD or 0.93 USD to 1 CAD. So you're best to just
change it in person.
Canada's coins are dollarized in the sense that they're mixed in and treated as par. Only vending machines in the USA will take them though,
and the penny was eliminated in 2013 since it cost double to make what it was worth. There's only nickels, dimes, quarters and 1 dollar and
2 dollar coins, Canadians call them "loonies" (picture of a loon, a duck like bird on the front) and "toonies" (there's a polar bear, but it comes
from being worth 2 "loonies"). The 2013/2014/late 2012 series $1 and $2 are a pain in the ass because the government changed their composition
so they weigh less than the earlier coins meaning they don't always work everywhere that's automated.
Don't change your currency at the airport! YYZ/YVR/YUL have terrible rates. Only $5+ bills are taken in the USA at banks btw, and lastly, if you
don't want to spend $40.00 USD to get from the airport to Toronto you can take the "192 Rocket" which lets you get to Kippling Subway Station
and take the subway for free too, it's $3.00 cash only, exact change and there's a stop at both terminal 1 and 3, (T2 is closed).