The OpenCL specification is maintained by the Khronos group. It can be found at
http://www.khronos.org/registry/cl/specs/opencl-1.0.43.pdf
The SIGGRAPH ASIA Khronos OpenCL presentation by Neil Trevett of NVIDIA can be found at
http://www.khronos.org/developers/library/overview/opencl_overview.pdf
There is a quick reference card for OpenCL 1.0 API that can be found at
http://www.khronos.org/files/opencl-quick-reference-card.pdf
This guide (The Nvidia OpenCL JumpStart Guide) will help you to start developing GPU accelerated applications today, using C for CUDA compute kernels and the CUDA Driver API in ways that that will make it easy to transition to OpenCL when you are ready.
The Nvidia OpenCL JumpStart Guide can be found at http://developer.download.nvidia.com/OpenCL/NVIDIA_OpenCL_JumpStart_Guide.pdf
AMD has put together an introduction to OpenCL that briefly goes over the anatomy of OpenCL 1.0 in its three main parts and shows a simple code example. It is not meant to be a detailed tutorial for OpenCL 1.0.
http://sites.amd.com/us/fusion/apu/Pages/fusion.aspx
