In my last job I was lucky enough to see a presentation by Goranka Bjedov (who works for Google) on performance testing. I just stumbled across the same presentation, available for free on video.google.com.
It's a terrific overview of the wide variety of tests that constitute "performance testing". It also does a good job of explaining the architecture and methodology associated with the execution and reporting of stress and volume testing.
She gives a good plug to the Jakarta JMeter project (http://jakarta.apache.org/jmeter/), although I recall Google have written quite a few in-house extensions to this product to make it work for them.
Finally, I enjoyed some of her war stories and real-life examples of things that you can find while performance testing.