gbulmash's Journal: Predicting How Much Slashdot Effect A Page Can Take?

What's the best way to measure a CGI script's usage of system resources (processor cycles, RAM) to predict how many users you can handle at once, or within a short time period, before your server is "slashdotted"? I figure there has to be a utility for stress testing a CGI-script or even a plain web page and measuring what levels of use start degrading performance and to what degree. So, any recommendations?