Apache Administrator's Handbook - Book by Rich Gowen covers all aspects of running an Apache server, starting with the installation, and going through configuration, security, dynamic content, and performance tuning.
Apache Cookbook - Companion site of a guide book written by Ken Coar.
Apache Desktop Reference - Companion site of an Apache reference manual, which is available here for download.
Berkeley Lab Computer Protection Program: Resources - A six step guide to securing an Apache Web Server. Covers obtaining a secure version of the software, operating system security, enabling features, server configuration, CGI interface and patching vulnerabilities.
Essential Apache for Web Professionals - Scott Hawkins's book handles virtual hosting, database connectivity - even complex session management and load balancing tasks.
Ricocheting.com - Installing and configuring Apache and ActivePerl in Windows.