Bikechain is a go-to spot for University of Toronto students (who can use all the services for free). This DIY repair shop and bike lending hub is also open to the general public on a PWYC basis.
The big space is stocked with all manner of tools and bike parts, as well as lender bikes for students. Bikechain regularly hosts public workshops and other events. It's best to book an appointment if you're heading in to do repairs.