Valve will be pushing an update to players in the "next couple of weeks" that will create a VR mode for Team Fortress 2. Anyone with a Rift dev kit and access to the game will be able to play it now, in the same servers everyone else in the public plays in. Initially this will only be on PC, but will be coming to Mac OS X and Linux platforms in the future.
Joe Ludwing, Valve programmer, felt that the Team Fortress game was the obvious first choice for this project.
The Team Fortress community is large and healthy. There are millions of people playing TF every week, but they're also used to us shipping a lot of updates.
Ludwig also said they are working on VR support for their other games as well, having already tested it a bit in Left 4 Dead and Half-Life 2, though he added they were no where near a point of being ready to ship.
The Oculus Rift is a VR headset that was successfully funded with Kickstarter and will ship to supporters in April. Pre-Orders are already available on the Oculus Rift website. You can check out the kickstarter video and longer panel video from SXSW below.