I've visited both the following Aikikai dojo in T.O. (just be sure to contact them beforehand if you're visiting) and have found the experiences quite rewarding:
Taught by Bob Zimmerman Sensei, a large dojo (member and space-wise) that also practices in Iaido as well.
Taught by Yumi Nakamura Sensei, a smaller but very friendly and helpful group with a nice space in a community centre. Highly recommended!
I also had the JCCC (Japanese Canadian Cultural Centre) recommended to me but as I was only in town for a couple of days over the holidays, they were closed at the time, so I didn't get a chance to visit them. http://www.jccc.on.ca
If you're so inclined, I also believe I did a couple of past blog/journal entries regarding my brief time training in Toronto.
Hope this helps!