Deep fryer with leftover oil

Let the oil cool completely, and then empty it into a plastic container with a lid, such as an empty margarine or cottage-cheese tub. Cover and find a "hazardous" waste location to dump it. You can also try to drop it off at a local restaurant, which should already have a correct destination to its large quantities. Never dump fat down the drain, since it can cause clogs. Plus, liquid and solid fats do not break down easily, an issue if you have a septic system.