Tsung stress testing tool

http://tsung.erlang-projects.org/

"Tsung (formerly known as idx-Tsunami) is a stress testing tool written in the Erlang language. It can currently stress test HTTP, PostgreSQL , SOAP and Jabber/XMPP servers. Tsung is distributed under the GPL license. Tsung can simulate hundreds of simultaneous users on a single system. It can also function in a clustered environment." (wikipedia description)