Google today announced that it has made video, voice and group chat easier to access from within Gmail.
One change is the presence of an icon for the voice and video chat plugin. If the person you're chatting with from within Gmail doesn't have that plugin, you can one-click the icon to issue them an invitation.
Extant features such as "Go off the record," "Block", and "Send SMS" are available above the chat window.
Unfortunately, these functions don't seem to extend to the Gtalk client. Unlike Skype's recent beta there is no group video chat.