Google has begun rolling out Internet phone service built into the interface of its Gmail service letting you make free video and voice calls within the US and Canada for the rest of this year. Call prices for other countries start at $0.02 per minute.
More information about this can be found on the Google blog post:
We’re rolling out this feature to U.S. based Gmail users over the next few days, so you’ll be ready to get started once “Call Phones” shows up in your chat list (you will need to install the voice and video plug-in if you haven’t already). If you’re using Google Apps for your school or business, then you won’t see it quite yet. We’re working on making this available more broadly – so stay tuned!