Here is a small collection of links to more information and opinions about the new Vulkan graphics API.
Vulkan talks and documents
Vulkan frontpage at Khronos
Vulkan overview by Khronos
Valves Vulkan talk at GDC 2015 (“glNext: The Future of High Performance Graphics”): Slides, Video on GDC Vault (free access)
Khronos Vulkan talk at GDC 2015 (“The new Vulkan and SPIR-V specifications”): Slides, Video ( old Video, worse image quality).
LunarG, the company that is implementing the Vulkan drivers for Intel GPUs on Linux, had a Reddit AmA.
Vulkan, SPIR-V and OpenCL talk by Nvidia at GPU Technology Conference 2015
SPIR-V (the shader binary of Vulkan and OpenCL 2.1)
Video about GLAVE: A Vulkan debugger developed by LunarG and Valve
Blogs and Forums
Imagination Technologies blog: Trying out the new Vulkan graphics API on PowerVR GPUs
AMD blog: One of Mantle’s futures: Vulkan
gtruc: Redefining the shading languages ecosystem with SPIR-V
Official Feedback Forum
My own first impression
Demos and Applications running on Vulkan (but also Mantle and/or DirectX 12)
Oxide Games and Stardock talk DX12, Mantle, and Vulkan (GDC 2015): Video
Mantle API Whitepaper (thanks to Jean-Baptiste Lepesme for the link)