There really are no herbs that will help with the thyroid long term. A thryoid condition is serious and should be treated by a medical doctor and not with over the counter remidies.
It will depend on the type of thyroid condition you have what type of herbal remedy may work for you. People who suffer from hypothyroidism, or under active thyroid, have been known to use Sage either in cooking or in teas for thyroid support. Hyperthyroidism, or over active thyroid is known to be helped by lemon balm.
I know someone who swears by Vaxa's Thyroid Formula which is an herbal and homeopathic. The herbs contained in it are: Black Walnut, Ginseng, Kelp, Mullein, Bayberry and it is also rich in minerals good for the thyroid such as calcium, iron, zinc and others.
For helping with a thyroid condition, a regular multivitamin should be taken everyday, as long as extra doses of B-Complex vitamins, Vitamin C and zinc.