Citrus peels are great for all kinds of culinary applications, but they also make wonderful deodorisers for things like and . You can even use them in your dishwasher. Just toss them (rind and whatever pulp is attached) into the silverware strainer and run a regular cycle with whatever load of dishes are ready for washing. The citrus will help break down the gunk on the inside of the dishwasher and clear out any lingering odours. As a bonus, the citric acid will also help get glassware sparkly clean.
After years of abusing the silverware strainer in my dishwasher by heaving forks, spoons, and knives at it, some parts of the plastic have finally broken away leaving larger holes for smaller utensils to fall through or get stuck. The easy fix was drop-in strainers that are just the right size to stay in place.