Cheat Codes for Everyday Life, and How to Use Them
http://www.wired.com/culture/culturereviews/magazine/17-05/st_cheatcodes
Insanely Simple Country Codes for International Calling
http://www.simplecountrycodes.com/

Insanely brilliant. Via @seldo.

Simple, elegant, and very useful. Brilliant.

Interesting, though the codebreaker did use a computer to solve it.

200 anos depois um texto criptografado é decodificado.

WSJ.com is available in the following editions and languages:

A cipher by Mr. Patterson. Simple to use without a computer, hard to crack.

For more than 200 years, buried deep within Thomas Jefferson's correspondence and papers, there lay a mysterious cipher -- a coded message that appears to have remained unsolved. Until now.

There are three levels of game play beginner, intermediate, and advanced. As students play games, they will learn Morse Code, complete brainteasers that involve math and logic, create their own cipher machines, crack Yardleygrams and cryptograms, and learn some words in different languages.

This site from the National Security Agency offers lots of information about ciphers and codes, and lets students test their skills at detection and code-breaking.

There are three levels of game play beginner, intermediate, and advanced. As students play games, they will learn Morse Code, complete brainteasers that involve math and logic, create their own cipher machines, crack Yardleygrams and cryptograms, and learn some words in different languages.