An excellent, highly readable cryptography reference book is Applied Cryptography: Protocols, Algorithms, and Source Code in C, Second Edition, by Bruce Schneier; ISBN 0471117099.
A great book on the SSL protocol, and especially useful if you are programming with SSL libraries, is SSL and TLS: Designing and Building Secure Systems, by Eric Rescorla; ISBN 0201615983.
OpenSSL project: http://www.openssl.org
ModSSL project: http://www.modssl.org
OpenBSD, a free Unix server operating system with a focus on security: http://www.openbsd.com
Apache reference, by the original author of mod_ssl: http://www.apacheref.com