What is the Islamic ruling regarding treatment of women at beauty parlors? What else is Haram (except removing eye-brow hairs)? Please clarify so that we may stop doing them.

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

A woman can use all kinds of cosmetics and she can beautify her self and any other woman can help her in this concern. Therefore, if there is any beauty parlor for ladies only, she can go there for the purpose of beautification provided one should stick to the rulings of Sharia such as not exposing her Awrah to anyone, not practising what is Haram like shaving eyebrows, making artificial space between teeth and imitating non-Muslims or wearing tight contour garments, etc.
Briefly, it is permissible for a woman to go to the beauty parlors to beautify herself as long as there is no transgression of the limits of Sharia.
Allah knows best.