Some links related to the hobby of code breaking
American Cryptogram Association
Code Penguin
Endeavour's page
The Rat's cipher page (Normor test)
Phoenix Society Puzzles
Mystery Twister
FOMALHAUT
JUDE's Headline Puzzles
Secret Code Breaker
Simon Singh
The Contest Center
National Cipher Challenge, UK
My other sites:
Bion's Gadgets
Encode-Decode