WWII carrier pigeon message discovered in Surrey chimney
If you like stories about Bletchley Park, which was the United Kingdom's main decryption establishment [Government Code and Cypher School (GC&CS)] during WWII, this might be interesting
Unfortunately, the message is very likely to have been encrypted with a one-time pad (http://en.wikipedia.org/wiki/One-time_pad). Unless the pad still exists it will be impossible to decrypt the message, though either the agent who sent it may be identified who could have always wondered about a missing message, and the message may have been sent again if they failed to get a response from it.