Cryptography Related Websites
National Security Agency
National Cryptologic Museum
The Secret Language by Ron Hipschman
Cryptography (good links)
Example Codes
An Application of Frequency Tables-Code Breaking
Letter Frequency Analysis
Enigma and the Code Breakers
Bletchley Park
Codes and Cyphers
Cryptology (Oliver Pell)
PGP Help Page
A Newcomer's Introduction to PGP