I am a huge fan of citrus fruit. I eat two or more a day. So I have lots of peels. Want a nice scent in your home? Toss one of those peels into a pot and turn it on to simmer.
For me, rather than burning the propane to keep the stove going for this air freshener I simmer it on my heater. Let me explain - I live in a house that tends to be very dry in the winter from a forced hot air heater in the living room. To combat this, we keep an old stainless steel saucepan filled with tap water on top of the vent. As the heat blows out the water evaporates into the air. Back when I was growing up in a house with radiators I can remember my parents having a container that hung over the radiator for the same purpose. I drop a citrus peel into this pot and we get a nice scent throughout the house any time the heater is running. It doesn't cost anything to heat the water this way (we have to heat the house anyway) and the peel from the yummy orange I ate for breakfast gets used a little before it is discarded.