Edgar Allan Poe often used codes and ciphers in his stories, most famously in "The Gold-Bug" (which incidentally inspired a very young William Friedman to take up an interest in cryptography). He also asked readers of one popular magazine to send him their ciphers to crack: which he (allegedly) managed to do for the hundred such that arrived.
However, in 1839 Poe published two tricky cryptograms allegedly by "Mr. W. B. Tyler" (probably a Poe pseudonym) which nobody at the time was able to break. These were rediscovered in 1985 by Professor Louis Renza, who then tried to raise their profile: before too long (in 1992), Professor Terence Whalen managed to solve the first one, which turned out to be nothing more complex than a simple monoalphabetic cipher.
The second (still-unbroken) cipher attracted the attention of Professor Shawn Rosenheim, who not only described it in his book The Cryptographic Imagination: Secret Writing from Edgar Poe to the Internet (Johns Hopkins, 1997), but also put up a $2500 prize to attract solvers' attention, with the help of Jim Moore of bokler.com who built a website to promote it.
And then, after Rosenheim and Moore had fielded hundreds of fruitless emails and responses, a software engineer from Toronto called Gil Broza finally cracked the second cipher in October 2000: his decryption is detailed here.
For followers of the Voynich Manuscript, this makes for fairly depressing reading: neither of the "W. B. Tyler" ciphers were, even by the standard of Milanese ciphers circa 1465, particularly tricky, yet Broza had to work really quite hard to solve the second one. He worked out his own transcription, wrote his own software... and then still basically had to break into it by hand, a process made even more difficult by the presence of errors in the ciphertext (which were probably introduced in the typesetting). And people wonder why modern supercomputers can't unravel the secrets of Voynichese - a cipher that is ten times harder than the second Poe Cipher.
The real mystery about Poe is actually the manner of his death: but that's an intriguing story for another day... :-)