Stumpled upon
JMeter, that I have tested during the day, and I am impressed with the amount of things that can be done with it! It is a performance testing/load generating application written completely in Java. It has a nice GUI, so you don't have to do any programming! The files generated are XML, so it's quite easy to do any external processing of the data captured. I recommend it, if you for instance need to verify a new server.