Some of these are to be taken with a grain of salt,

your mileage may vary:

_______________

Harder:

- Anatomy of Security-Enhanced Linux (SELinux)

- Understanding AppArmor

- grsecurity

- What is Linux Security Module?

- 10 Basic Linux Security Tips to Implement

- The Best Linux Security Tools

- Linux Audit and Intrusion Detection

- The Unix security audit and intrusion detection tool

- Top 100 Network Security Tools

- The short life and hard times of a Linux virus

- LIDS Secure Linux System

- 10 ways to secure your Linux desktop

Better:

- Beautiful Conky Setup

- Building a Better (Linux) GPU Benchmark

- Last-Exit: A Better Linux Client for LastFM

- The best Linux system repair distribution

- A Better Introduction to Linux User Interface

- Better Linux Dock

Faster:

- How to make Ubuntu extremely fast

- Booting Linux in five seconds

- Improving boot time on a general Linux distribution

- Reboot Linux faster using kexec

- Make Linux Faster and Smoother

- A better, faster desktop search for Linux

- 10 ways to make Linux boot faster

- Fast file copy in Linux

- How fast does Arch Linux install? (video)