Lavender is the most widely used essential oil in aromatherapy, particularly for its relaxing properties. Try placing two drops on a handkerchief by your pillow when you are trying to sleep.
As Lavender blends very well with many other oils, try the following: 3 drops of Lavender, 3 drops of Mandarin and 1 drop of Geranium in a teaspoon of Sweet Almond oil added to a warm bath before a long, relaxing soak.