Our tipline just lit up with news that the faction change service discussed so often recently is now available! At least in the US, anyway. One of our super secret to-be-announced new bloggers from the EU mentioned that he doesn't see it overseas yet, but Rogue specialist Chase Christian is already swapping his Rogue over. Hopefully Europe will have it very soon.
The faction change (accessed via your account management page), in addition to allowing you to flip from Horde to Alliance (and vice versa) also seems to include the ability to change anything else you could change through a character recustomization, such as a name change for the price of $30. We have some picture of the process incoming, so keep an eye on this spot. We'll have them put together for you in just a moment.
Update: And here are the images of the process. Enjoy!
Update #2: The faction change FAQ has some additional details you might find interesting. There are some mount/reputation restrictions when you switch over that you might want to be aware of before you drop your $30.
Gallery: Faction change feature