I tend to disagree with Rod (and perhaps due to the time passed since the publising of this book) that the Microsoft Web Application Stress Tool is better than JMeter. JMeter was extremely easy to setup (after just skimming the manual to learn the terminology) and it is very flexible as well. Microsoft hasn't put out a new version of their test tool since 2000, where as JMeter is an active jakarta project. There is no question I would recommend JMeter to any developers looking to give their bosses good output reports for load testing. Additionally, it can handle all sorts of protocols and requests, including FTP, SOAP and so forth. Definitely check it out:
http://jakarta.apache.org/jmeter/