[*] Google Talk

[Bill Reid]

It is nice that Google has gone with Jabber as the IM protocol but I do not see 
any discussion about the voice protocol. They say they are working with 
Earthlink and sipphone to "federate" their services. I do not know if that means 
that the voice protocol is SIP-like. They allow other Jabber clients but only 
Google Talk for the voice service.

http://www.google.com/talk/developer.html

-- Bill