A Course in Number Theory and Cryptography, by Neal Koblitz, Springer-Verlag: A more advanced mathematical treatment.
Introduction to Cryptography, PGP freeware introduction to the whole security infrastrucure - but no math.
Python.org/doc: The official documentation, (starts with the Tutorial for programmers) and links to many other resources
The remaining links are more for programming beginners, but they might be useful:
Hands-on Python Tutorial: My tutorial for Comp 150 - very slow, for total beginners, does not get to writing classes.
http://people.csail.mit.edu/pgbovine/python/, a cool site to visualize execution. Good for the newbie, but also useful for class and object concepts.
Http://Codingbat.com/python Coding practice site. Intro programming level.