Someone finally managed to perform the Wheeler beam-splitting test of quantum mechanics. It works as predicted. How an experimenter chooses to set a second beam splitter affects the "reality" of a photon at the first beam-splitter, even if the choice is made after the photon has already passed the first device. Interpret it anyway you like--causation backwards in time, selection among alternate universes, whatever--it's still fascinating.
UPDATE (Jan 11): It's only tangentially related, but interesting that some in the U.S. Army are talking about eventually shifting from the electromagnetic spectrum to quantum communications.