CrypTool-Online (CTO) runs in a browser and provides a huge variety of encryption methods and analysis tools including many illustrated examples.
Land der Ideen - Statements
"The non-numerate students found the pictorial descriptions of how the various processes work invaluable. They speak of CrypTool helping to remove their fear of the subject. A few have even reluctantly admitted that CrypTool brought the subject to life and made it fun."