http://www.magentocommerce.com/magento-connect/Magento+Core/extension/1359/magento-compiler
A plugin for magento that is meant to boost performance. Free.
http://www.nbs-system.co.uk/blog-2/magento-optimization-howto-en.html
Very useful article outlining the broad basics of optimising Magento. Includes links to more detailed information and lots of config file examples. Very useful.
http://www.fabrizio-branca.de/magento-caching-internals.html
Very detailed article explaining how Magento implements its caching mechanism. It seems to be some custom classes layered on top of Zend's caching framework. Useful read.
http://markjaquith.wordpress.com/2006/02/13/adventures-with-wp-cache2-apc/
Using APC (Alternative PHP Cache) and WP-Cache2 together causes some issues, the solution is to have APC not cache the wp-cache-config files.
http://www.connectedinternet.co.uk/2006/06/18/guide-to-optimizing-wordpress-servers/
June 2007 - A guide to optimising WordPress sites, focusing on MySQL and PHP caching techniques.
http://blog.circlesixdesign.com/2007/01/22/diggproof/
January 2007 - A guide to optimising a server for WordPress hosting, focusing on MySQL and PHP caching techniques.
