To create 2D FBO using single cubemap face, we could use glFramebufferTextureFace: http://www.opengl.org/sdk/docs/man4/xhtml/glFramebufferTextureFace.xml
However this is not implemented on NVidia drivers (259.39).
I was albo unable to use glFramebufferTextureLayer for this purpose (got GL_INVALID_OPERATION error generated. <texture> does not name a layered texture.). I was however successful with simple glFramebufferTexture2D using GL_TEXTURE_CUBE_MAP_POSITIVE_X + face.
Is this driver bug or spec bug?
See also http://www.opengl.org/discussion_boards/ubbthreads.php?ubb=showflat&Number=280943#Post280943