Now, Google adds voice and video chat to Gmail for Ubuntu and other Debian-based Linux users! To get started you have to download a plugin (downloads at the end) and install it then it will work as Google Talk on your Gmail, iGoogle, or orkut with voice and video chat!
As announced it will support RPM soon, you can download the plugin from the link below and have fun with video and voice chat,
Download Google Voice and Video Chat for Linux