This is a great repellent to use on people and also to spray around the yard for outdoor parties. Make a strong tea of pennyroyal leaves in a pint of water. Alternatively, you can dilute oil of pennyroyal in water. Spray this on your body, clothing, etc.

Another good recipe is to take citrus rinds, especially lemon and orange, and make a strong tea of them, using half a cup of chopped rinds to a cup of water. Simmer for 20 minutes and cool before using. This is especially effective against ants.