Linux: Many Linux users love to accomplish as much as they can utilising only the command line structure in Terminal. CenterIM lets you chat with your friends on GTalk, Jabber, Windows Live Messenger, Yahoo Chat, or AIM. Aside from the novelty, it is extremely resource-light and makes it easy to chat via SSH.
Other useful features include a plethora of keyboard shortcuts for those who dislike mice and the ability to function as a full-screen terminal window to avoid distractions. Google Talk isn't listed as one of the compatible chat applications, but you can easily use Jabber to connect to GTalk. One thing I really like is that at the bottom of the screen is listed the most popular keyboard shortcuts.
All in all it's a solid program. I suspect many will try it for the gimmick of having command line chat, but I also suspect many of those will keep using the program once the novelty has worn off.
CenterIM is a free download for Linux systems at the source link below. Ubuntu users can simply click on this link to begin installation.