As former Toronto resident I have to chime in, too!
Don't forget Casa Loma (
www.casaloma.org), Royal Ontario Museum, and also that Art Gallery on Dundas (I can't remember the name), Hockey Hall of Fame (if you're interested in hockey), SkyDome and/or Air Canada Centre for sports.
Go to King Street to see great theatre like The Lion King or Mamma Mia.
Hummingbird Centre has ballet and opera, and stuff like musicals like Beauty and the Beast.
If you like comedy go to Second City Theatre on Blue Jays Way.
Go to Danforth Avenue to see Greektown (and I am talking souvlaki, not fraternities
)
Go to College Street to see Little Italy.
I think that's about all I can think of right now.
www.toronto.com is a great resource too.
Cele, here is the Gamma Phi Beta Collegiate Chapter's website:
http://gammaphibetato.tripod.com/
You can even have a house tour (and I would have to say that the Gamma Phi Beta house has one of the most beautiful interiors, for sure!)