Mike B's set
squish for the web: http://www.froglogic.com/products/evaluate.php
Lisa TEST: http://www.itko.com/products/lisatest.jsp
AppPerfect Web Test: http://www.appperfect.com/products/app-test.html
Selenium: http://seleniumhq.org/
Felicia's set
Watij - http://watij.com/
TestMaker - http://www.pushtotest.com/
Sahi - http://sahi.co.in/w/
Yawet - http://www.informatrix.ch/indexYWT.html
Ed's Set
Yui Test with Selenium driver
Alex's Set
Sean's Set
Dave's Set
Tools that emulate a browser
Yawet (all OS's that support Java)
Tools that make record a user journey in browser and then let the tester modify the test
Yui Test
Selenium
Func Unit
TestMaker
Sahi
Tools that use existing browsers but force the user to write code for each test