Kerbal Space Program is a space simulator. It allows you to build rockets and planes, and fly them to space, and beyond! Think it would be a great contender for VR? Well, it is, and here's how to get it working!
The how-to for this is fairly easy. The program necessary for this is Tridef3D. Setup instructions for Tridef3D are on it's page.
Recommended Plugins/Mods Edit
There are a few mods that will make your Kerbal Rift experience much better, and easier!
KerbTrack is a mod that allows the use of a tracker to control the camera in Kerbal Space Program. They have added Oculus Rift support to it as well! HOWEVER, I was not able to get it working in the version of Kerbal Space program I was playing. If you can get it working, please edit this on how to do so.
Raster Prop Monitor (RPM) Edit
RPM is a quintessential mod for first person flying, especially with the Oculus Rift! What it does is add a whole bunch of useful knobs and meters that are necessary for accurate space travel. Extremely recommended!
Fly safe, fellow Kerbonauts!