Vulkan 1.0 specification has just been released (three hours ago).
It has been a long wait, but it looks it deserve. Specially when OpenGL driver execution is your main bottleneck.
Most of official documention from Khronos Group is available in Github (docs, samples)

Intel, nVIDIA, AMD, Imagination (PowerVR), Qualcomm and others have released tons of content: articles, samples, demos and... new Vulkan drivers!.

Here you can find a list with all the graphic cards that have passed conformance tests. At first sight,  nVIDIA GeForce graphic cards higher than 640(M / GTX) accomplish all the requisites; so, all gamers with a three-years-old (or newer) card can be happy :-)

nVIDIA has been specially active in Vulkan divulgation and promotion. :-)

A brief list of programming resources:

• LunarG Vulkan SDK
• Vulkan GPU Hardware Database
• GPUOpen Vulkan (AMD) with software, articles
• Presentations
• Vulkan overview (Feb'16)
• GDC 2016 
• nVIDIA -- High-Performance, Low-Overhead Rendering with OpenGL and Vulkan
• nVIDIA -- Vulkan and NVIDIA The Essentials 
• Siggraph 2015
• nVIDIA -- Vulkan on NVIDIA GPUs (slides, video)
• Intel -- Vulkan on Intel Graphics (video)
• Khronos –Vulkan Overview
• GTC 2015
• Khronos API Standards Update: Including Vulkan, OpenCL 2.1 and SPIR-V (Video)
• Tutorials
• AMD – Vulkan Renderpasses 
• nVIDIA – Open-Source Vulkan C++ API 
• nVIDIA – OpenGL like Vulkan 
• nVIDIA – Transitioning from OpenGL to Vulkan 
• nVIDIA – Vulkan Memory Management 
• nVIDIA – Vulkan Shader Resource Binding 
• Programming and Code samples
• Khronos – Vulkan Registry 
• Khronos – Vulkan 1.0 Quick Reference 
• Khronos – Vulkan API Reference Pages 
• nVIDIA – Vulkan on Android 
• nVIDIA – Vulkan Choppers 
• nVIDIA – Open-Source Vulkan C++ API 
• nVIDIA – OpenGL and Vulkan comparison on rendering a CAD scene using various techniques 
• VulKan ToolS (examples, docs)
• Examples and demos for the new Vulkan API