My SANS MGT414 CISSP class is about to study the Cryptography domain. An excellent resource that I recommend to anybody learning about Cryptography is Cryptool:
"CrypTool is a free, open-source e-learning application, used worldwide in the implementation and analysis of cryptographic algorithms. It supports both contemporary teaching methods at schools and universities as well as awareness training for employees and civil servants. "
Cryptool lets you see and interact with several different cryptographic methods, which reinforces the theory that we learn in the textbooks.