There's a new feature in town for Gmail Chat, but it's actually not all that new. It's been possible for some time now to go into "invisible" mode via AIM and other chat protocols, but Gmail Chat is finally joining the invisible party.
Going invisible through chat software enables IMers to log into their IM accounts without showing that they've logged on. It's still possible for others to IM you, though it's unlikely since you wouldn't be listed as "online", and you can also IM others.
Invisible mode in Gmail Chat doesn't yet work with Google Talk, the gadget and desktop app. Currently, it's only supported via the online Gmail interface, but we're sure that'll change soon.