since year 2008 there comes a new module called cacherouter. which is born from the following module/projects: APC, fastpath_fscache, Memcache, and XCache.

beside general enabling the module, there is a configure step has to be done.
Installation
1. Enable the module in admin/build/modules.
2. Setup your settings.php

this module is avaliable for drupal 5.x and 6.x at http://drupal.org/project/cacherouter
CacheRouter is a caching system for Drupal allowing you to assign individual cache tables to specific cache technology. CacheRouter also utilizes the page_fast_cache part of Drupal in order to reduce the amount of resources needed for serving pages to anonymous users.