What can I use to do load testing or functional testing of my web server?

Here are some links to open source web server load and functional testing programs or frameworks:

• ab (Apache Benchmark): http://httpd.apache.org/docs/2.0/programs/ab.html
• Canoo: http://webtest.canoo.com/webtest/manual/WebTestHome.html
• JMeter (Apache JMeter): http://jakarta.apache.org/jmeter/
• Selenium: http://www.openqa.org/selenium/
  • a short screen movie demonstrating a functional testing framework called Selenium: http://zachs-mac.lrc.txstate.edu/~zach/selenium_in_action.mov
• http://simpletest.sourceforge.net/Simple Test – unit testing for PHP

• List of 23 Open Source Performance Testing Tools http://opensourcetesting.org/performance.php