After residing in West Bengal for more than quarter of a century, I was quite sure that I knew most of the things about durga puja. I knew that I had very little knowledge of the rituals, but I was sure that I knew most of the stories related to Durga Puja. Then I visited wikipedia's page on durga puja, and was astonished to realize that I know so little about durga puja. Here is the summary of the contents at wikipedia’s.

Durga puja (Bengali: ‘Worship of Durga’), also referred to as Durgotsava (Bengali: ‘Festival of Durga’), is an annual Hindu festival in South Asia that celebrates worship of the Hindu goddess Durga. It refers to all the six days observed as Mahalaya, Shashthi, Maha Saptami, Maha Ashtami, Maha Navami and Bijoya Dashami. The dates of Durga Puja celebrations are set according to the traditional Hindu calendar and the fortnight corresponding to the festival is called Devi Paksha (Bengali: ‘Fortnight of the Goddess’). Devi Paksha is preceded by Mahalaya and is ended on Lokhi Puja (Bengali: ‘Worship of Goddess Lakshmi’).

One of the Asuras, Mahishasura, in the form of a buffalo, grew very powerful and created havoc on the earth. Under his leadership, the Asuras defeated the Devas. The world was crushed under Mahishasura's tyranny, the Devas joined their energies into Shakti, a single mass of incandescent energy, to kill Mahishasura.

A very powerful band of lightning emerged from the mouths of Brahma, Vishnu and Shiva and a young, beautiful female with ten hands appeared. All the Gods gave their special weapons to her. This Shakti coalesced to form the goddess Durga. Riding on a lion, who assisted her, Durga fought Mahishasura. The battle raged for nine days and nights. Finally on the tenth day of Ashvin shukla Paksha, Mahishasur was defeated and killed by Durga.

Daksha, the Lord of the Earth, and his wife Menaka, had a daughter called Sati. As a child, Sati started worshipping Lord Shiva as her would-be-husband. Lord Shiva was pleased with the Sati's worship of him and married her. Daksha was against their marriage but could not prevent it. Daksha arranged a yagna to which everyone except Lord Shiva was invited. Sati, feeling ashamed of her father’s behavior and shocked by the attitude meted towards her husband, killed herself. Lord Shiva was anguished when he discovered this.

In her next birth, Sati was born as Parvati or Shaila-Putri (First form of Durga), the daughter of Himalaya. Lord Narayana asked Shiva to forgive Daksha. Ever since peace was restored, Durga, with her children Saraswati, Lakshmi, Kartikeya, Ganesh and her two `sakhis` - Jaya and Vijaya - visit her parents each year during the season of `Sharatkal` or autumn when Durga-Puja is celebrated. In the Krittibas Ramayana, Rama invokes the goddess Durga in his battle against Ravana.

In West Bengal it is the biggest festival of the year. Not only is it the biggest Hindu festival celebrated throughout the State, but it is also the most significant socio-cultural event in Bengali society. The prominence of Durga Puja increased gradually during the British Raj in Bengal. After the Hindu reformists identified Durga with India, she became an icon for the Indian independence movement. In the first quarter of the 20th century, the tradition of Baroyari or Community Puja was popularized due to this. After independence, Durga Puja became one of the largest celebrated festivals in the whole world.

Initially the Puja was organized by affluent families since they had the money to organize the festival. During the late 19th and early 20th century, a burgeoning middle class, primarily in Calcutta, wished to observe the Puja. They created the community or Sarbojanin Pujas.

These Pujas are organized by a committee which represents a locality or neighborhood. They collect funds called "chaanda" through door-to-door subscriptions, lotteries, concerts etc. These funds are pooled and used for the expenses of pandal construction, idol construction, ceremonies etc. Major Pujas in Calcutta now derive almost all of their funds from corporate sponsorships. Community fund drives have become a formality. Pujas in Calcutta and elsewhere experiment with innovative concepts every year. Communities have created prizes for Best Pandal, Best Puja, and other categories.

Durga Puja also includes the worship of Shiva, Lakshmi, Ganesha, Saraswati and Kartikeya. Modern traditions have come to include the display of decorated pandals and artistically depicted idols (murti) of Durga, exchange of Bijoya Greetings and publication of Puja Annuals.

In Bengal, Durga Puja is also called Akalbodhan (Bengali: 'untimely awakening of Durga'), Sharadiya Pujo (Bengali: ‘autumnal worship’), Sharodotsab (Bengali: ‘festival of autumn’), Maha Pujo (Bengali: ‘grand puja’), Maayer Pujo (Bengali: ‘worship of the Mother) or merely as Puja or Pujo.

The actual worship of the Goddess Durga as stipulated by the Hindu scriptures falls in the month of Chaitra, which roughly overlaps with March or April. This ceremony is however not observed by many. The more popular form, which is also known as Sharadiya (Autumnal) Durga Puja, is celebrated later in the year with the dates falling either in September or October. Since the Goddess is invoked at the wrong time, it is called "Akaal Bodhon" in Bengali.

While the most recent revival of the Autumnal worship of Goddess Durga can be traced to revivalist tendencies in the early freedom movement in Bengal, the first such Puja was organized by Raja Nabakrishna Deb of the Shobhabazar Rajbari of Calcutta in honor of Lord Clive in the year 1757. The puja was organized because Clive wished to pay thanks for his victory in the Battle of Plassey. He was unable to do so in a Church because the only church in Calcutta at that time was destroyed by Siraj-ud-Daulah.

Today, the culture of Durga Puja has shifted from the princely houses to Sarbojanin (literally, "involving all") forms. The first such puja was held Guptipara - it was called barowari (baro meaning twelve and yar meaning friends)

Durga puja mood starts off with the Mahishasuramardini – a two-hour radio programme that has been popular with the community since the 1950s. Bengalis traditionally wake up at 4 in the morning on Mahalaya day to listen to hymns from the scriptures from the Devi Chandi. During the week of Durga Puja, in the entire state of West Bengal as well as in large enclaves of Bengalis everywhere, life comes to a complete standstill. In playgrounds, traffic circles, ponds—wherever space may be available—elaborate structures called pandals 'are set up, many with nearly a year's worth of planning behind them. The word pandal means a temporary structure, made of bamboo and cloth, which is used as a temporary temple for the purpose of the puja. While some of the pandals are simple structures, others are often elaborate works of art with themes that rely heavily on history, current affairs and sometimes pure imagination.

Somewhere inside these complex edifices is a stage on which Durga reigns, standing on her lion mount, wielding ten weapons in her ten hands. This is the religious center of the festivities, and the crowds gather to offer flower worship or pushpanjali on the mornings, of the sixth to ninth days of the Devi Paksha. Ritual drummers – dhakis, carrying large leather-strung dhak show off their skills during ritual dance worships called aarati. On the tenth day, Durga the mother returns to her husband, Shiva, ritualized through her immersion into the waters –– Bishorjon also known as Bhaashan.

Today's Puja, however, goes far beyond religion. In fact, visiting the pandals recent years, one can only say that Durga puja is the largest outdoor art festival on earth. The sculpture of the idol itself has evolved. The worship always depicts Durga with her four children, and some banana-tree figures. In the olden days, all five idols would be depicted in a single frame, traditionally called pata. However, now the trend is to depict each idol separately.

At the end of six days, the idol is taken for immersion in a procession amid loud chants of 'Bolo Durga mai-ki jai' (glory be to Mother Durga') and 'aashchhe bochhor abar hobe' ('it will happen again next year') and drumbeats to the river or other water body. After this, in a tradition called Vijaya Dashami, families visit each other and sweetmeats are offered to visitors (Dashami is literally "tenth day" and Vijay is "victory").Durga Puja commemorates the annual visit of the Goddess with Her children to Her parents' home, leaving finally on the Dashami to be re-united with Shiva. This leaving ceremony is symbolized by the immersion of the idols on Dashami.

The entire process of creation of the idols (murti) from the collection of clay to the ornamentation is a holy process, supervised by rites and other rituals. On the Hindu date of Akshaya Tritiya, clay for the idols is collected from the banks of a river, preferably the Ganges. After the required rites, the clay is transported from which the idols are fashioned. An important event is 'Chakkhu Daan', literally donation of the eyes. Starting with Devi Durga, the eyes of the idols are painted on Mahalaya or the first day of the Pujas. Before painting on the eyes, the artisans fast for a day and eat only vegetarian food. Many Pujas in and around Kolkata buy their idols from Kumartuli, an artisans' town in north Calcutta.

In 1610, the first Durga puja in Kolkata was supposedly celebrated by the Roychowdhuri family of Barisha. Though this was a private affair, community or ‘Baroyari’ Durga puja was started in Guptipara, in Hooghly by 12 young men when they were barred from participating in a family Durga puja in 1761. Since then, community pujas in Bengal came to be known as ‘Baroyari – ‘baro’ meaning 12 and ‘yar’ meaning friends. The Indian freedom struggle also had an influence on Durga puja in Kolkata. In 1926, Atindranath Bose initiated the first ‘Sarbojanin’ Durga puja in which anybody, irrespective of caste, creed and religion, could participate in the festivities. This was consciously done to instill a feeling of unity.

Pandals and idols inspired by a particular theme have been the hallmark of many community or Sarbojanin Pujas in Kolkata. Puja committees decide on a particular theme, whose elements are incorporated into the pandal and the idols. Popular themes include ancient civilizations like the Egyptians or Incas. Contemporary subjects have also been the subject in some pandals. The budget required for such theme-based pujas is often higher than traditional pujas. They attract crowds and are well-received.

Rapid growth of competitiveness in theme pandals, has also created a cultural backlash from city's traditional Puja pandals, which now claim, "We do not do theme puja, we do Durga puja", according to one hoarding put up in Salt Lake, Kolkata.

A gathering of friends called “Aadda” in Bengali is common in many homes and restaurants. A lot of shopping is done, and retailers cash in on this opportunity with special offers. Visiting pandals with friends and family, talking and sampling the food sold near them is known as pandal hopping. Young people embrace this activity. The whole city of Kolkata glows in light and late night revelers throng the streets of Kolkata during Durga Puja.

Bengalis celebrate with new clothes and other gifts, which are worn on the evenings when the family goes out to see the pandals. Although it is a Hindu festival, religion takes a back seat on these five days: Durga Puja in Bengal is a carnival, where people from all backgrounds, regardless of their religious beliefs, participate and enjoy themselves to the hilt.

In Kolkata alone more than two thousand pandals are set up, all clamoring for the admiration and praise of the populace. The city is adorned with lights. People from all over the country visit the city at this time, and every night is one mad carnival where thousands of people go 'pandal-hopping' with their friends and family. Traffic comes to a standstill, and indeed, most people abandon their vehicles to travel by foot after a point. A special task force is deployed to control law and order. Durga Puja in Kolkata is often referred to as the Rio Carnival of the Eastern Hemisphere.

One of the oldest puja of Devi Durga which I could find was Durga Puja of 4 Ghosh Lane, Kolkata - from 1856

The oldest puja are in North Kolkata, like Baghbazar Sarbojonin, Kumartuli, Ahiritola, Md. Ali Park, College Square.

Source: Wikipedia
http://en.wikipedia.org/wiki/Durga_Puja
http://en.wikipedia.org/wiki/Vijayadashami
The above article is a edited and summarized version of the article at wikipedia