- http://www.thefrontside.net/crosscheck - browser environment emulator.
- http://jsmock.sourceforge.net/ - mock objects - not sure what to make of this - runs with jsunit test runner.
- http://www.openqa.org/selenium-core/usage.html - usage overview.
- http://www.openqa.org/selenium-ide/ - Selenium IDE is a firefox plugin for interactive development and running of tests.
- http://wiki.openqa.org/pages/viewpage.action?pageId=763 - has some more useful background summary.
- http://www.getfirebug.com/ - Firebug
- MS script debugger for IE