Regular reader and contributor Gebhard sent us a pointer to Crypto 101, an "introductory course on cryptography, freely available for programmers of all ages and skill levels" by Laurens Van Houtven (lvh) available for everyone, for free, forever. It's a pre-release PDF read of a project that will be released in more formats later. 

The Crypto 101 course allows you to learn by doing and includes "everything you need to understand complete systems such as SSL/TLS: block ciphers, stream ciphers, hash functions, message authentication codes, public key encryption, key agreement protocols, and signature algorithms."

• Learn how to exploit common cryptographic flaws, armed with nothing but a little time and your favorite programming language.
• Forge administrator cookies, recover passwords, and even backdoor your own random number generator.

Lvh has written a fine book here, it's comprehensive yet accessible, robust but not overwhelming, and accomplishes its intended mission as a learning guide. And did I mention that it's free? Every aspect of the project is hosted on Github, and includes exercises for hands-on. It really is a 101 opportunity to learn and develop your skills, I highly recommend your immediate acquisition and review.