Xibalba & WebVR
My game Xibalba already provided a stereo rendering mode and supported an external tracking server to get orientation updates from the VR headset, but it was clumsy and only worked for the old Oculus Rift DK1. So I decided to ditch the old stereo rendering mode and implement WebVR proper.
WebVR handles the distortion for the Headset by itself. All you have to do is render your game into a side-by-side stereo format and request fullscreen mode on your Headset. Orientation updates are provided by a nice, clean API that's easily implemented in the game.
Play the game here: phoboslab.org/xibalba/
If you have a DK2 but no WebVR enabled build of Chrome or Firefox, you can also try a standalone Windows version of the game. It's essentially a Chromium build bundled with the game and batch file to start it. Makes it a bit easier to get going.
Download: xibalba-vr.zip ~80mb