From your cl::Device comment I assume you mean a C++ API reference? I don't know if a document describing the C++ API is ready yet, largely because the API is still somewhat in flux. I've always found that the comments in the header combined with the OpenCL spec itself is a satisfactory combination. After all, the C++ code is feature for feature a direct mapping to the C API, but with some cleaner interfacing to deal with some of the less pleasant features of a C API.
ETA: The forum parses emoticons by default, how annoying...
