CoScripter: Simplify Web-based Processes
CoScripter is a new experimental Firefox extension by IBM that allows you to automate manual process that you do on the web. So, for example, if your bank forces you through a couple steps to get to your bank balance then you can use CoScripter to handle all the clicks and forms for you.
You could also use it as a form of semi-automated web testing, in a similar manner to Selenium, except that it would be more limited. For quick and dirty testing of your site's functionality it should be more than enough.