Today is the Hindu festival Diwali. It is a major festival that celebrates the victory of good over evil. As this site indicates, "Diwali is called the Festival of Lights and is celebrated to honor Rama-chandra, the seventh avatar (incarnation of the god Vishnu). It is believed that on this day Rama returned to his people after 14 years of exile during which he fought and won a battle against the demons and the demon king, Ravana. People lit their houses to celebrate his victory over evil (light over darkness). The goddess of happiness and good fortune, Lakshmi, also figures into the celebration. It is believed that she roams the earth on this day and enters the house that is pure, clean, and bright. Diwali celebrations may vary in different communities but its significance and spiritual meaning is generally 'the awareness of the inner light'."
In the Jain religion, a similar festival this night celebrations the attainment of liberation (moksha) by the founder Mahavira. It is also the Sikh holiday Bandi Chhor Divas, which celebrations the liberation of the sixth guru, Guru Hargobind and 52 other princes from prison. In Buddhism, the day is Ashok Vijayadashami, the day when Emperor Ashoka converted to Buddhism. See this site and this site for more details on the holidays.