The Faculty of Graduate Studies provides information about housing on campus (Keele & Glendon) with basic, but useful information and links to off-campus housing:

The following link brings you directly to housing options on the Keele campus:

Places4Students is a site which tailors apartment and roommate listings to areas close to university and college campuses in North America:
York University page
University of Toronto (downtown) page

Online sites, such as Craigslist, Kijiji, PadMapper, and ViewIt list various rentals and at least can provide one sense of types of availabilities and rentals amounts:
Craigslist housing
Kijiji real estate (use list on left side: “room rental, roommates” & “apartments, condos”
Toronto Rentals
Rent Seeker

Some students have also had success with different Facebook groups, which one must first join, such as:
Toronto Prospective Renters
Homes for Queers Toronto
Bunz Home Zone

Additionally, always check the Toronto Bedbug Registry