The idea for VoxOx is that it encompasses all of your communication in one app. Phone calls, IRC, instant messages, SMS, social networks and so on, are handed through VoxOx's client. The big news at CES was that the VoxOx client was updated, and VoxOx told me that the Mac version is being reworked according to feedback to look more like a Mac app, according to the Apple HIG. Once inside the app, it's quickly apparent that VoxOx is powerful -- you can merge contacts from multiple networks and even keep conversations going across protocols. There is a charge to call out (just like Skype), but there's never a charge for inbound calls, so family and clients can call your computer directly, and/or you can get those calls routed off to any other number. There's even a translation service now integrated into the client, so you can see real-time translations of chats back and forth to other countries.
Unfortunately, VoxOx's biggest issue is that it's not very open -- you can't pull in contacts from another app, and you definitely can't bring them out of the service easily. The UI looks better than it used to, I'm told, but it's still not what I'd call a "beautiful" app. Still, if you're looking for a way to consolidate voice communications, VoxOx seems a compelling option.
The company told me that a new version of the app would include icons in each chat window to let you know exactly which protocol chat messages came from, and that a version of the app had already been submitted on the iOS App Store (though they were currently dealing with all of the "song and dance" that Apple requires for approval). As I spoke with them, the Mac App Store had just opened up for business, and putting a release up there is something that they're considering, though they hadn't made a decision yet.
If you find yourself seeking a solution for interfacing with a lot of different communication protocols quickly (and don't mind putting in a little bit of time and effort to dedicate yourself to one final network), VoxOx could be what you're looking for. You can download the latest version, still technically called a beta, on the company's website.