Gtalk as we know is Google’s AIM, a simple and lightweight Messenger. However, it lacks some features compared to Yahoo Messenger and MSN. The Gmail chat has the option to go Invisible. but there’s nothing like “Invisible Mode” in Gtalk yet to keep annoyers at bay.
But what one can do is set the status to “Always idle” and pretend like they are away from PC. gAlwaysIdle is one such tiny software that will help to do the same.
Works on Windows XP and Vista ( no 64-bit Operating Systems).
Download gAlwaysIdle : Click Here (112KB)
you can also find some extra features on the labs version of other Google products which allows you to make yourself invisible but it does not always override the gtalk client software if you have that installed
http://mwolk.com/blog/how-to-stay-and-chat-invisible-and-as-offline-in-gtalk/
@Abhimanyu
Yes dude i read your post, right now Gtalk still in its basic stages. In future they might add more features including the invisible mode.