Handbook of Applied Cryptography by Menezes, van Oorschot, and Vanstone is freely-available online. This is a comprehensive reference of many
basic cryptographic primitives.
Introduction to Modern Cryptography by J. Katz and Y. Lindell (Chapman & Hall/CRC 2008) - good textbook covering cryptography from a modern perspective.
Mathematical Recreations and Essays by W. W. Rouse Ball. This is a free e-book. Chapter 11 (written by A. Sinkov) is an excellent survey of classical ciphers.