Valve has released an experimental virtual reality mode for Steam. The mode works with Oculus Rift and can be used by dev kit owners now.
Valve's Joe Pudwig states on the Steam forum
that, "As of the most recent Steam Client Beta steam now supports an experimental VR mode. If you own an Oculus Rift dev kit you can try it out by starting Steam with "-vr" on the command line. Then press the Big Picture button to enter Big Picture + VR mode.
"The first time you run you may need to do the following:
1) Run Steam in the desktop client without the -vr option
2) Find "SteamVR" under "Tools" in your library. (If you don't have it installed, install it.)
3) Bring up properties on SteamVR and opt-in to the "Beta Update" beta. Let the update download.
4) Quit the Steam Client again and start it with -vr"
Valve also looks set to unveil a virtual reality SDK for Steam Machines at the Steam Dev Days conference, which starts today. There's speculation that Valve is working on its own VR hardware, though it's expected to also support Oculus Rift, which today's release seems to bear up.