IBM just released another good article form the Redpaper series : «Tuning Red Hat Enterprise Linux on IBM eServer xSeries Servers». Haven't read it yet, but looks really cool.
Table of Contents
Chapter 1. Understanding Linux Performance
Chapter 2. Monitoring tools
Chapter 3. Tuning the operating system
Chapter 4. Analyzing performance bottlenecks
Chapter 5. Tuning Apache
Chapter 6. Tuning database servers
Chapter 7. Tuning LDAP
Chapter 8. Tuning Lotus Domino