Latest issue of Linux Journal is completely dedicated to Drupal. You will find a lot of really interesting articles in it.
One of them is my article about cache in Drupal, where I describe how it works and how to use it. I also compare performance of different cache backends and describe some techniques that will help you to make your website run faster.
Linux Journal is offering this Drupal special issue as a free download. Please download it, read it and let me know what you think about it.