Toolkit for multithreading and OpenGL

is there a multithread-safe OpenGL toolkit which allows multiple OpenGL contexts (one for each thread)? I need to support multiple windows, each one with its own OpenGL rendering. Each window corresponds to a thread, so far no toolkit has shown to be useful for this. Any ideas?

Try Producer, it specifically design to multi-threaded, multiple graphics rendering ontop of OpenGL. Its what we use in OpenScneeGraph to provide this support.