Coursera.org offers a great course on cryptography. You can check it here: https://www.coursera.org/course/cryptography
Not only you will be able to learn a lot, Coursera will also help you to test your learning by giving you some tests.
Web Security/Network Security Basics
Coming down some books, there is one good book called Gray Hat Hacking, The Ethical Hackers Handbook, 3rd Edition by Allen Harper. This book is recommended for newbies and is easily available in almost every bookstore.
Another book on web security is Web Application Security, A Beginner's - by Bryan Sullivan
However, I will not suggest you to buy and start reading these books without any prior knowledge. You must first work on improving your programming skills, learning C/C++. PHP, Python, Java and Ruby will help you a lot, and networking skills, basic knowledge of TCP/IP will help you a lot.
You might also want to learn ASM (Assembly language) for developing exploits and reverse engineering.
There is a website called http://opensecuritytraining.info/, which provides free tutorial on various aspects of the information security. You can try that also.