• Use mint as a fly repellent. Small sachets of crushed mint can be placed around the home to discourage flies.
• Bay leaves, cloves and eucalyptus wrapped in small cheesecloth squares can be hung by open windows or doors.
• Place a small, open container of sweet basil and clover near pet food or any open food in the house.
•  A few drops of eucalyptus oil on a scrap of absorbent cloth will deter flies. Leave in areas where flies are a problem.

Source: www.eartheasy.com