I remember Dave linked to a story a long time ago about "number stations." These are shortwave broadcasts that have been on the air for decades. They feature only a single voice reading lists of seemingly random numbers. These number stations are widely believed to be a method for spy agencies to communicate with their agents in the field. NPR did a story on them recently. Slashdot had a story today about The Conent Project which is releasing a 4 CD set of these recordings, and sponsering a cryptograpic challenge to crack the code behind these numbers. Assuming they are not using a one time pad, which would be unbreakable, I can't wait to see what these numbers mean.