The Shravan month in a Hindu lunar calendar is one of the most auspicious months and numerous pujas and rituals are held in this month. One of the most important puja in the month is the Varamahalakshmi Puja which held on the last Friday of the Shukla Paksha of Shravan month. Apart from this another puja and ritual dedicated to Mahalakshmi is held on the first Friday of the Shukla Paksha of Sawan month.
In some regions a murti of Goddess Lakshmi is installed on the first Friday of Shravan Shukla Paksha for puja. It is believed that Goddess Lakshmi only visits those houses that are clean. The houses are cleaned and offerings are made to Goddess Lakshmi. In some regions this is a community puja in which women of neighborhood gather in a house and perform the puja.
But the most important puja is the Varamahalakshmi puja. You can find details of Varalakshmi Puja here in this article.