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
"On the one hand, CrypTool has very efficient implementations including cryptanalysis and all relevant standards. So the tool is technically very useful. On the other hand, the visualization and presentation of the cryptographic techniques in CrypTool is excellent and there is no system that I know of that combines those two qualities in such an outstanding way."