Today is Nobo Barsha, Bangla for New Year, also known as "Pahela Baishakh". This marks the beginning of Baisakh, the first month of Bengali calendar. It is usually marked by the tradition of "Halkhata", opening of books of accounts for the new year by the village traders. The celebration of Pahela Baishakh by broad masses in the Bangladesh context may be dated from the observance of the day by "Chhayanat", a cultural organization in 1965. In an attempt to suppress Bengali culture, the Pakistan Government had banned tagore songs. Protesting this move, Chhayanat opened their Pahela Baishakh celebrations at Ramna Park with Tagore's song welcoming the month. The day continued to be celebrated in East Pakistan as a symbol of Bengali culture. After 1972 it became a national festival, a symbol of the Bangladesh nationalist movement and an integral part of the people's cultural heritage.
A bit of history about Pahela Baishakh from Wikipedia:
Celebrations of Pahela Boishakh started from King Akbar's reign (sixteenth century). The main event of the day was to open a halkhata or new book of accounts. This was wholly a financial affair. In villages, towns and cities, traders and businessmen closed their old account books and opened new ones. They used to invite their customers to share sweets and renew their business relationship with them. This tradition is still practised, especially by jewellers.
From the Banglapedia:
New year's festivities are closely linked with rural life in Bengal. Usually on the day everything is scrubbed and cleaned. People bathe early in the morning and dress in fine clothes and then go to visit relatives, friends and neighbours. Special foods are prepared to entertain guests. Baishakhi fairs are arranged in many parts of the country. Various agricultural products, traditional handicrafts, toys, cosmetics as well as various kinds of food and sweets. are sold at these fairs.
The Daily Star termed it "Bangalees' biggest carnival". Check out their special supplement.
Wishing everyone a happy Bengali New Year (1414), a happy Thai New Year (Songkran) a happy Combodian New Year (Maha Songkran) and a belated happy Easter.