JCrypTool (JCT) is an open-source e-learning platform, allowing to experiment comprehensively with cryptography on Linux, MAC OS X, and Windows.
Land der Ideen - Statements
"CrypTool already provides a strong basis for educational activities and there is great merit in continuing this development. There is scope for adding new algorithms, [...], and new cryptanalytic methods as they emerge. In summary I feel that CrypTool can play a very fruitful role in education about cryptography, and thus have a positive impact on this field in general."