Both of these contain citric acid, so their rind is great for polishing brass, copper and other non-ferrous metals.
Sprinkle on a little baking soda to get an even better result. Or pop a few slices of rind in a bottle of vodka to create a fantastic and flavoursome infusion.

Adding citrus peels to olive oil will not only flavour it, but will help to reinvigorate oil that’s getting old.
To rid your microwave of nasty smells, put lemon peel and any remaining lemon juice with the same amount of water in an uncovered bowl and boil gently for up to ten minutes.