Happy Diwali/Deepawali to all you bhaktas!
Here is part of an article about Deepawali from www.indiayogi.com
"The most common legend related to Diwali is from the epic of the Ramayana (a legendary story of Lord Rama). King Dashratha had three wives namely Kaushalaya, Keykayee and Sumitra and four sons Rama, Bharat, Laxmana and Shatrughan. Rama was the son of Queen Kaushalaya and Bharat was the son of Queen Keykayee. Keykayee wanted Bharat to be the next King while the King Dashratha wanted Rama, his eldest son to be the King. But Keykayee made full use of the two wishes King Dasharatha had once promised Keykayee and asked for sending Rama to exile for the period of fourteen years. During that time Lord Rama fought and won tenuous struggles in the south part of the Indian sub-continent (which some people believe is now Sri Lanka) killing the king of Demons, Ravana who had forcibly taken away his wife Sita. Diwali marks his victorious return to his kingdom, Ayodhya.
Another reason for the celebration of Diwali is that it marks the killing of the evil Narkasura at the hands of Krishna (a Hindu God). Naraka is believed to have abducted 16,000 women. Krishna killed him and rescued these women whom he later married. Naraka is the personification of hell and is believed to be the monsoon during which all activities come to a stand still.
In South India, the story widely associated with Diwali is that of Narasimha, the man-lion incarnation of Vishnu. According to a legend, Hiranyakshipu was an evil demon king. He was unjust and cruel to his people. However, he was almost invincible, having extracted a boon from Brahma (the creator) that he would be killed neither by beast nor man, neither inside nor outside, neither during the day nor at night. When his atrocities became unbearable, the gods sought Vishnu's help. Assuming his fifth incarnation of Narasimha, the man-lion, Vishnu killed Hiranyakshipu with his claws in the courtyard just before daybreak, hence steering clear of the boundaries of the boon.
Diwali or Deepawali is celebrated for a period of five days. The First day is called Dhanteras or Dhantrayodashi, which falls on the thirteenth day of the month of Ashwin. 'Dhan' means wealth and this day is generally observed to acknowledge and welcome wealth. Lakshmi the Goddess of wealth (wife of Lord Vishnu-the preserver) is believed to enter houses on this day, therefore entrances are made colourful with lovely traditional motifs of Rangoli (designs made with coloured powder) to welcome the Goddess of wealth and prosperity. To indicate her long-awaited arrival, small footprints are drawn with rice flour and vermilion powder all over the houses. Lamps are kept burning all through the nights, since Lakshmi is said not to enter a dark house. The lamps also welcome home the spirits of dead ancestors, who are believed to visit on this auspicious night. In addition, the light frightens away any evil spirit that might be wandering about near the house on this night. In the state of Orissa, lamps are lit to light up the dark path so the spirits of ancestors can find their way back to heaven. In modern times, diyas have been replaced by wax candles and colored electric bulbs. In villages cattle are adorned and worshipped by farmers as they form the main source of their income. Cows are offered special veneration as they are supposed to be the incarnation of Goddess Lakshmi and therefore they are adorned and worshipped on this day."