Some departments or research groups provide in-house imaging services. Most departments provide local photocopiers and a mechanism for charging work-related copies to the appropriate account. Ask your advisor for information. Some advisors have their own photocopiers and prefer to have students use them. Copies made as a teaching assistant can generally be charged to a class account, which the professor can provide. You might also want to ask if you can get a personal copier code to use for your own course work.
If these resources aren't available, or if you have more extensive needs than what your department offers, there are other places you can go. Public photocopiers are available in the Engineering Library. If you will be making many copies, there are cheaper places in Collegetown or downtown. Some of your options are described here.