Wondered why can’t you set “Invisible” status in your Google Talk program? And still want to hide your online status from some of your Gtalk contact list then here are some tips to stay in invisible offline mode in Gtalk desktop client and the Google mail web interface!
Gmail web Invisible mode
If you do not want to block people and still want to chat with some of your friends in gtalk list then make use of Gmail.com web interface, you will have the option to set an invisible mode and chat from the left sidebar.
Gtalk Offline via Lab Edition
Basically the desktop Gtalk client doesn’t allow you to set invisible offline status so one tip you can try out is by downloading the Gtalk Lab edition (Download lab edition) which is a google talk desktop client with a lot of features unavailable in the Gtalk gadget (the one which we use regularly).You can also launch orkut, google calendar with a click on a button using the lab edition and use those cute smileys bar in the chat window.
Another way to show offline status to your friend’s is to make use of multi protocol chat client for mac and windows but I prefer the lab edition as it is light and developed for users who wants to connect with only Google friends 
