Durgashtami is observed on the eighth day of the waxing phase of moon (Shukla Paksha) of Aswhin month. Also known as Mahashtami, it is the eighth day of the Navratri and Durga Puja celebrations. Durgashtami 2010 is October 15. A fast is observed on the day by man devout Hindus. Weapons of Goddess Durga are also worshipped on the day.
Note - In Malayalam Calendars followed in Kerala, Durga Ashtami is marked on October 14, 2010. The tithi begins here on October 14 and ends on October 15. Navami is marked on October 16, 2010.
On Durgashtami day the 64 Yoginis and Ashtanayikas, the eight consorts of Durga, are also worshipped. Goddess Shakti temples perform special pujas and rituals on the day.
The day is also observed as Astra Puja as weapons of Goddess Durga are worshipped on the day.
The day is also known as Virashtami as there are displays using arms and martial art performances.
You can get more details of Durgashtami in this article.