I've been working on web site performance optimizations lately (though you might not believe it when visiting this site...)
I've come across a few useful performance-related resources that I've been using lately:
- Optimizing Page Load Time–An excellent overview of many issues that can affect web site performance
- Online web page benchmarking tool (webpagetest.org)
- Benchmarking APC vs. eAccelerator using Drupal (2bits.com)