Looks like Google now has a Jabber server running, linked to your Gmail account. To login using GAIM:

screen name: tbarik
server: gmail.com
password: gmail-password

I’m not going to speculate on what this means, but I just find it highly amusing that Ben, who is working on MSN Messenger Server at Microsoft, brought this topic up just last week with me:

Ben: I like MSN. Interview for Messenger Server.
Titus: Just put jabber on it and call it a day.
Ben: Jabber servers don't scale.

Ben, we’ll see about that.

Update: Google Talk is now available, and there are instructions for connecting with GAIM.