I have a lemon tree, too. My favorite is lemon custard and lemon ice cubes in my glass of water.

For an air freshener, I occasionally put the lemon peels (smaller pieces are best) in a pot of water, bring it to a slight boil and then turn of the heat. The fragrant oils evaporate easily out of the lemon skins as the water cools. I love the lemon scent! There are probably better recipes out there, but the key is to use the lemon peels.