Today, 5 September 2011, Mahalakshmi Vrat begins in North India. It is observed for 16 days, starting on Shukla Paksha Ashtami. Dedicated to Goddess Maha Lakshmi, Mahalakshmi Vrat ends on Krishna Paksha Ashtami in Ashwin month. It is mainly observed in Delhi, Bihar, Jharkhand, Madhya Pradesh & Uttar Pradesh.
Mahalakshmi Vrat Katha and the importance of this vrata is mentioned in Bhavishya Purana as a conversation between Yudhistira and Lord Krishna.
Here is the detailed guide for Mahalakshmi Puja Procedure.