Oregano; good for fighting coccidia, salmonella, infectious bronchitis avain flu, blackhead and e-coli.
Lavender; stress reliever, increases blood circulation and is an insecticide.
Mint; insecticide and rodent repellent.
Calendula; laying stimulate and can add colour to the egg yolk.
Borage; high in vitamin A, C and calcium.
Tansy and nasturtiums; parasite prevention.
Comfrey; rich in calcium, phosphorous, potassium, iron and copper.
Lemon balm; anti-viral and anti-bacterial. May be a rodent repellent.
Most of this plant information comes from the Lifestyle Block's How to care for your poultry vol 2 (a fantastic resource book that everyone who has or wants chickens should own!).
So far only Chive (she just loves the herbs! and is so funny to watch as she tries to put her head through the wire to get to the herbs) and Nero are eating the herbs but I'm sure the other girls will eat them as they need.