Way back when, Vonage was the leading competition to Skype for a piece of the early VoIP market. While Skype has prospered since in the UK, less has been heard of Vonage over here. But it's still around, especially in the US, and now offering you this iPhone and Android app for free, Facebook-based calling.Vonage is essentially offering VoIP based around your Facebook network, which theoretically is your social circle. In practice? Well, perhaps not. But let's go with it for now. Calls are made over Wi-Fi and 3G and require both parties to have the Vonage software installed. If that's the case, press 'talk' and you'll be chatting away for free, data charges permitting of course. It also works worldwide, so if Uncle Brian has emigrated to Australia, keeping up with the latest news is both easy and cheap.If it works for Facebook, other social networks could be targeted, so you might have that long-forgotten work colleague catching up via LinkedIn soon enough. In the meantime, if your Facebook friends really are friends, give it a whirl over there.