I just stumbled upon this cool website which has tons of Sun TV programs online. You can watch many serials like Arasi, Kolangal, etc online for free.
The videos are streamed and hence, there is a time lag at times. But sure it is close to watching Live Streaming Sun TV for free online.
For those of you who don't know what Sun TV is all about - well, Sun TV is a very popular Tamil TV channel watched by millions of tamils across the world.
The site where you can watch Sun TV programs is : http://www.dailymotion.com/aranetworld/1
