Penetration testing
Let's throw in a couple of superb guides to help test our sites and server to the limit.
ISECOM's OSSTM
Acronyms galore, the Open Source Security Testing Methodology Manual from the Institute for Security and Open Methodologies offers training plus a raft of resources:
OWASP Testing Guide
The Web Application Penetration Testing Project, again from OWASP, sets out best practices and, while focused mainly for an enterprise level audience, makes for an important if fairly steep read for all of us:
