The major Toronto parts/accessories dealers usually put fairly big booths up. JRP, BC Auto, etc... Sometimes you'll find deals, sometimes not. Depends on what you are looking for.
I've found there are a lot of "little guys" there who are willing to chat and give real-world accounts of what works and what doesn't. Small booths from small shops who may not have a huge selection of stuff or the best prices (sometimes they do though!), but have been around and experienced what works and what does not.
Again, this is all mixed in with the rice, hotrods, boom bass cars, lowriders, pickup trucks with airbrushed graphics, kit car Ferraris, etc, etc, etc...