Google Talk can can be accessed in a number of ways be it through Gmail or through Gtalk or through web messengers. Another way of accessing is to use sidebar in Firefox. GTalk sidebar extension is a Firefox add-on which enable you to access Gtalk from your Firefox sidebar.
Steps to access Gtalk in Firefox:
1. Download and install the add-on from the add-on website.
2. Right click on the top of Firefox toolbar, where buttons are located and select Customize.
3. Drag and drop the Gtalk toolbar into Firefox. Click on the Gtalk button once its available in the toolbar. On clicking Gtalk is enabled in the sidebar of your Firefox.
This add-on is specially useful for sending email also. You can enable/disable sidebar with ALT+G keyboard shortcut.This add-on is also useful for people who are not able to access Gmail or Gtalk in office or schools.