This September is going to be packed with celebrations! Onam was celebrated on the 2nd of this month in Kerala, and there is Dasara to look forward to. For people from Bengal, it is a frenzy of celebrations of Durga Puja at the end of the month. Listed here are the fairs and festivals for this month.
Dasara or Navaratri. Dasara or Navaratri is celebrated from 19th to 28th September. Although Dasara is celebrated in many parts of the country, it is a grand state sponsored function in Mysore, that culminates with a procession of elephants on the 10th day. See http://www.mysoredasara.com/ for details. It is also a popular festival in Coorg. Navaratri is celebrated with many public functions and dance programs in the state of Gujarat.
Kullu Dasara. Unlike in rest of the country, Dasara in Kullu begins when it concludes in other places. It begins on 28th September and goes on for 10 days. See more details at http://kullu.net/culture/cl111.html
Durga Puja. The most celebrated festival of Bengal begins on 25th September and concludes on 28th September. Kolkata is the best place to see the celebrations.