"Transliteration is the practice of transcribing a word or text written in one writing system into another writing system. It is also the system of rules for that practice."

Google Transliteration - almost accurate and easy to use... available in Hindi, Tamil, Telugu, Kannada, Malayalam...

Some useful purposes:

->if u dont have anything to do, try transliterating some meaningful ;) movie songs like the one below...

"arachha maava araippoma... thuvacha thuniya thuvaippoma... a emma emma emmamma"

"அரச்ச மாவ அரைப்போமா... துவச்ச துணிய துவைப்போமா... ஏ எம்மா எம்மா எம்மம்மா"

->if u want to scold someone in your native language over chat... "podaa panni" "போடா பண்ணி"