This large, modern zoo has more than 5000 animals, with stars such as pandas, rhinos and polar bears. (There are no elephants, though, because they are so difficult to maintain in captivity humanely.) The zoo even tweets the hours when visitors can meet its newborn animals. It's 34km west of downtown Toronto; the 86A Toronto bus route (6am to 8pm) goes to the zoo from Kennedy station daily in summer, weekdays only at other times.
On-site parking costs $12. The website has details of discounted admission through the CityPass, which includes the CN Tower and other sights.