i knew you could do this but never tried. so i did it today and it works like charm.
If your like me and use GAIM as an IM client, then you might want to follow these instructions for setting up GAIM to use the GoogleTalk servers.
1. Click Accounts->Add (at the login screen)
2. Under the protocol dropdown choose “jabber”
3. Your screenname is everything before @gmail.com
4. Change server from jabber.org to gmail.com
5. Click show more options
6. Make sure “USE TLS if available” is checked.
7. Connect server should be “talk.google.com”?
8. Password is the same password that you use for gmail