Hindi, Urdu, Indian English and English
"Bollywood is the informal term popularly used for Mumbai-based Hindi-language film industry in India."
"Bollywood is commonly referred to as Hindi cinema, even though "Hindustani", understood as the colloquial base common to both Hindi and Urdu, might be more accurate. Bollywood consists of the languages of Hindi, Urdu and English. The use of poetic Urdu words is fairly common. Some Bollywood films such as Mughal-E-Azam are entirly in Urdu. There has been a growing presence of Indian English in dialogue and songs as well. It is not uncommon to see films that feature dialogue with English words and phrases, even whole sentences. There are a growing number of English films."
"Dialogues are usually written in an unadorned Hindi or Hindustani that would be understood by the largest possible audience. Some movies, however, have used regional dialects to evoke a village setting, or old-fashioned courtly Urdu in Mughal-era historical films. Contemporary mainstream movies also make great use of English. In fact, many movie scripts are first written in English, and then translated into Hindi."
"Bollywood song lyrics, especially in the old movies, frequently use Arabo-Persic Urdu vocabulary."
"Bollywood" : http://en.wikipedia.org/wiki/Bollywood