Probably the best single source of information on this topic is by Dan Kegel. He keeps this information at his Cal Tech alumni Web site. Here's the URL:
http://alumnus.caltech.edu/˜dank/fixing-overloaded-web-server.html
The Apache project also has some decent information on this topic.
http://www.apache.org/docs/misc/perf-tuning.html
Additional sources of information are linked from both of these URLs.