The rumors were of course true, Google Talk was announced today.
(sidebar: I always wonder how these things first get noticed since they're rarely mentioned on Google's homepage)
Much like Skype, Google Talk combines text chat and voice communication. But at first glance I don't see anything similar to Skype Out or Skype In which allows you to connect to "real world" telephone lines. More info here.
(sidebar2: I love the little sample text on the screenshot "I hear they're building an IM/Voice service...")
Google Talk is built on the Jabber protocol and Google addresses their desire to use open technologies. And like a lot of Google applications, they're opening up a lot of the guts to developers.