Recently I worked on a site that required a lot of modules, and when we moved it to our customer's production server it literally took seconds to load a page. Removing modules was not an option.
Many people would just say that Drupal is bloated and slow and leave it at that. Sure with a plain vanilla LAMP installation and loads of Drupal modules things can get slow. But don't let that discourage you.
The following are my favorite Drupal performance hacks, with their advantages and disadvantages:
