PBS
Pbs Nova: Send a Coded Message Virtual Enigma
Explore the NOVA's Virtual Enigma machine used during WWII. You can send an encrypted message to a friend along with the special key needed to decipher the message. A link is also included to the Virtual Enigma.
Shodor Education Foundation
Shodor Interactivate: Caesar Cipher
Create your own affine cipher for encoding and decoding messages. Input your own constant and multiplier, then input a message to encode.