The MozVR team at Mozilla maintains their own site where you can try WebVR demos and find resources http://mozvr.com/
Currently, WebVR supports the Oculus Rift (DK2) and Google Cardboard. Support for other HMDs, such as the HTC Vive and the OSVR headset may be added in the future.
You can get WebVR running on a Samsung Gear VR headset, but it is not easy to do. See Using WebVR with the Gear VR headset.
The WebVR API is relatively simple. Here are some helpful resources and articles
- https://aframe.io - An open source web framework for building WebVR experiences.