I was always using skype for my voice chat, But i dont know for whatever reason i couldnt do it in the Ubuntu distribution. So today i came acroos empathy IM client. Though i wasnt sure of configuring skype in that i was able to configure gtalk in that.
Install Empathy by doing the following
System->synaptic Manager-> in search tab type empathy->select empathy for complete installation
for using empathy
goto Applications->internet->empathy IM Client
click on empathy->edit-> Accounts(F4)-add ur gmail user name and password.
Thats it!!!! get ready to do a voice chat with your friends.
it works perfectly fine in my ubuntu 9.10(Karmic koala)
Enjoy!!!