Skype is included in the 2.1.0 Update (for the Pre Plus).
On my Pre3 Google Talk is included, but as far as I can see only for simple text messaging. I'm able to add a Skype account in the phone settings, but I can't add a Google Talk account.
XDA Developers was founded by developers, for developers. It is now a valuable resource for people who want to make the most of their mobile devices, from customizing the look and feel to adding new functionality. Are you a developer?