On the Ibuildings techPortal today there's a new episode from their Dutch PHP Conference 2009 recordings series, Rob Allen's talk on caching and performance.

More, now than ever, websites need fast response times and be able to cope under load. As web pages contain more and more dynamically generated content, the challenge is on for PHP developers to develop efficient caching solutions. This presentation will focus on using caching techniques that can be used in a PHP project to increase the performance of a web site

Rob's talk looks at a few different means for caching and gives some "before" and "after" statistics to show how much of a difference each of them makes. You can either listen via the in-page player or you can download the mp3 directly.