Post Updated on 17-Apr-2010. The earlier instructions were not needed on the new Pidgin anymore. Pidgin has now added a new Google Talk protocol which can be used to configure your Google Talk id.
Pidgin (earlier Gaim) is a multiple protocol Instant Messenger client which can be used to chat using MSN, Yahoo, AIM, Google Talk and many other protocols.
How to configure Pidgin to work with Google Talk (Use Pidgin to chat with your GTalk friends)
- Download & Install the latest version of Pidgin. On Kubuntu / Ubuntu you can just type
aptitude install pidgin
in terminal to install Pidgin.
- Open Pidgin and go to Accounts –> Manage Accounts –> Add window of Pidgin.
- From the drop-down box choose Google Talk as the Protocol.
- For the Screen name enter your Google Id (Gmail Id) just the user name without the @gmail.com in it.
- In the Password field enter your Google ID password.
That’s it. Now you can start chatting with your GTalk buddies using Pidgin while keeping in touch with users of other IM users also. No need to install GTalk software. 
Let us know if you have any problems configuring it.