Server-side core documents
Powering the AMP in LAMP, here are the security stops for Apache, MySQL, and PHP. The L, by the way, is for dear old Linux, as previously linked.
Apache HTTP Server Version 2.2 Documentation
The home of Apache's official documentation for the latest-greatest release:
Apache: Module Index
Yeah, it's linked from the previous page, but in case you were feeling lazy ...
MySQL: Security
The official security scope for MySQL: