We show how transformation media [J. B. Pendry, D. Schurig, and D. R. Smith, Science 312, 1780 (2006); U. Leonhardt and T. G. Philbin, cond-mat/0607418] map quantum electromagnetism in physical space to QED in empty flat space. As a consequence, the Casimir force of left-handed dielectric media may become repulsive and may possibly levitate ultra-thin metal foils.