The University of Toronto is a big place - and old... so there is a lot to choose from. Anyways here is a selection of some of the different Colleges and other important buildings..
University College
Trinity College
St. Michael's College
Victoria College
Innis College
Robarts Library (freakin' massive library - and the building that the University replaced the old Frat Row with)
Hart House (kinda a community/student/faculty centre - with a handy rifle/pistol range in the basement
)
Soldier's Tower (memorial tower attached to Hart House with a museum/memorial room & carllion - it's where I'm a curator/guide)
Convocation Hall (home of graduation ceremonies and the largest classes in Canada - around 1200/lecture... and for those that saw 'Mean Girls' this is the site of one scene)