For all you desis who aren't totally fluent in the mother tongue, here's a useful guide to insults in many languages. I would list some of them here, but you've really got to see them to believe the wealth of creativity involved in cursing. The best ones are at the bottom of each page.

How to insult people in: Hindi, Punjabi, Bengali, Gujarati, Urdu, Kannada, Malayalam, Marathi, Tamil and Telugu.