You're on the right track when you say you need voice and remote desktop software, irrespective of whether you're going to be using Visual Studio or other tools to collaborate. I don't use Visual Studio myself, so I can't answer the part of your question about any tools integrated with it, but I do work as part of a distributed team and there are a whole heap of choices out there for you to pick from.
For VoIP, Skype is a common choice and one I've used a lot in the past, but I have to say I'm not a great fan of what it's become (ads and the beautiful simple interface has been replaced with a rather counter-intuitive one), so I tend to use either Trillian to talk to my Skype contacts, or C3 (which is actually intended for online gamers but is also great for general VoIP communication, is much less of a resource and bandwidth hog and is completely free). I found Google Talk's "feature" of asking you "Are you still there?" after a couple of hours while you're clearly still talking a bit annoying, as there's usually no point in keeping the tab in the foreground, so often we missed the question and got thrown out. Quality-wise, there wasn't much between the three on a broadband connection; if anything, I'd give the edge to C3.
As for web conferencing (or desktop sharing) software, which you'll need in order to view each other's desktops and control each other's mouse/keyboard for paired programming, I've used Netviewer commercially (my client had a license) in the past (before they were bought up by Citrix) and more recently TeamViewer, which is similar from a pure desktop sharing point of view but seems to have a few less features (or maybe I just haven't discovered them yet). We are also considering OpenMeetings but I haven't used it much yet so can't make an informed recommendation on that one.
Wikipedia's comparison pages seem to be kept quite up-to-date if you'd like more options to pick from:
Most of the commercial ones tend to have at least free trials, so make sure you try before you buy.
Once you've got the right tools set up, there's not that much difference between doing XP while sitting next to each other and while sitting in different parts of the world. (And there are actually benefits, e.g. you can't knock over the other guy's coffee cup and you can keep your own favourite keyboard and mouse settings.)