It looks like you're going to be able to log into Facebook from your PlayStation 3 in the near future as the folks at CVG have gotten confirmation
from Sony that the service will be coming to the PlayStation's XMB bar in the near future. Of course you could always log into the site using the system's in game browser but where's the fun in that. It's hard to imagine that Twitter support for the PlayStation 3 isn't too far behind as it's pretty damn simple to create a Twitter application using the provided API with the only hard part building it into the system's hardware. We'll let you know more as soon as we hear it.