Kuan Yin (觀音; Pinyin: Guān YÄ«n) is the bodhisattva of compassion as venerated by East Asian Buddhists, usually as a female. She is also known as the Chinese Goddess of Compassion by many. Kuan Yin originated as the Sanskrit AvalokiteÅ›vara, which is her male form. Commonly known in the West as the Goddess of Mercy, Kuan Yin is also revered by Chinese Taoists as an Immortal. The name Kuan Yin is short for Kuan-shih Yin (Py.: Guānshì YÄ«n, 觀世音) which means “Observing the Sounds of the World”.
 In Japanese, Kuan Yin is pronounced Kannon (観音) or more formally Kanzeon (観世音); the spelling Kwannon, based on a pre-modern pronunciation, is sometimes seen. In Korean, this incarnation of Buddha is called Gwan-eum or Gwanse-eum, and in Vietnamese, the name is Quan Âm or Quan Thế Âm Bồ Tát.
Kuan Yin is the Chinese name for the Bodhisattva Avalokiteśvara. However, folk traditions in China and other East Asian countries have added many distinctive characteristics and legends. Avalokiteśvara was originally depicted as Buddha when he was still a prince, and therefore wears chest-revealing clothing and may even sport a moustache. However, in China, Kuan Yin is usually depicted as a woman.
 In China, Kuan Yin is usually shown in a white flowing robe, and usually wearing necklaces of Indian/Chinese royalty. In the right hand is a water jar containing pure water, and in the left, a willow branch. The crown usually depicts the image of Amitabha Buddha, Kuan Yin’s spiritual teacher before she became a Bodhisattva.
There are also regional variations of Kuan Yin depiction. One of these is that of Kuan Yin with fish. In this depiction Kuan Yin is depicted as a maiden dressed in Tang dynasty style clothing carrying a fish basket. This is popular in the Fukien region of China.
Along with Buddhism, Kuan Yin’s veneration was introduced into China as early as the 1st century CE, and reached Japan by way of Korea soon after Buddhism was first introduced into the country from the mid-7th century. (from http://en.wikipedia.org/wiki/Kuan_Yin)
From Goddesses and Heroines by Patricia Monaghan:

It was said that Kuan Yin was so concerned for humanity that, upon receiving enlightenment, she chose to retain human form rather than transcend it as pure energy. And so she would stay until every single living creature attained enlightenment. Her name translates “she who hears the weeping world”; Kuan Yin sat on her paradise island P’u T’o Shan answering every prayer addressed to her. The mere utterance of her name in prayer was said to assure salvation from physical and spiritual harm. Even better was the observance of Kuan Yin’s own testimony of peace and mercy; her most devout worshipers ate no flesh and lived entirely without doing violence to other beings.

Sometimes it was said that Kuan Yin originally lived on earth as Miao Shan, a young woman of unearthly virtue. Although her father wished her to marry, Miao Shan decided to visit a monastery, which, contrary to her expectations, was a hotbed of vice. Her father, hearing of her presence in the convent and suspecting the worst, burned it to the ground. A rainbow carried her to heaven, where her innocent death earned her transmutation into the divine world. (from http://www.hranajanto.com/goddessgallery/kuanyin.html)

Kuan Yin’s birthday is celebrated on the 19th day of the second, sixth and ninth lunar month. Bake a sweet cake and lay it before her, or pour a bowl of milk in her honor. Light a stick of incense – flower-scented or sandalwood are especially please.
Most importantly: contemplate compassion and its role within your life. Work with the heart chakra, to open and cleanse it completely, allowing you to give – and receive – compassion’s gift in your life.