From what was a Wikipedia Category Unsolved Ciphers and is now included in Undeciphered Historical codes and ciphers - 'A list of unsolved problems that are, or are thought to be, codes or ciphers.'

  • Beale ciphers
  • The Blitz ciphers
  • D'Agapeyeff cipher
  • D-Day carrier pigeon cipher
  • Dorabella Cipher
  • European Voynich Alphabet
  • Fenn treasure
  • Kryptos
  • Papyrus Oxyrhynchus 90
  • Ricky McCormick's encrypted notes
  • RSA Secret-Key Challenge
  • Shugborough inscription
  • Taman Shud Case
  • Voynich Manuscript
  • YOGTZE case
  • Zodiac Killer

These are described further on the other Voynich Wiki [1].

There are many websites on the subject of uncracked codes and ciphers - eg [2], [3] and the Elonka's List page [4]. The lists share many entries in common.

See also Ciphers, Useful websites and materials and Undeciphered writing systems