Hammerhead is a stress testing tool for Web sites. It initiates connections from multiple IP aliases and simulates a user from each alias. It is fully configurable, and there are numerous other options for creating problems with a site. Extensive data collection is also available.
PureLoad is a load testing tool that simulates thousands of users executing requests against server based applications. It can be used to verify that your application will meet the expected performance criteria. PureLoad reports quality and performance problems, as well as detailed statistics gathered during a load test. PureLoad also includes extensive support for easy recording and testing of Web-based applications. The HTTP Recorder ease the process of capturing HTTP and HTTPS requests into PureLoad scenarios. The Web Crawler is used to scan a static Web site for general errors, and it can also be used to generate PureLoad scenarios to be used in a load test.