Every once in a while a new feature is added to Gmail. The features are usually announced on a Google blog post and quickly picked up by the blogosphere. That's exactly what happened with Gmail's new "Call Phone" feature. 

If you're a Gmail user, and you have the voice and video plugin installed, you'll see a "Call phone" option in the "chat" section of Gmail. To make a call, you just click the link and an overlay with a dial pad pops up. You can either search your contacts, or dial the number using the pad. 

I've had a couple problems making outbound calls, where it says that the user I was calling ended the conversation, but the call was never placed. When this happens, I hit the "redial" button and the call goes through.