Todd Ditchendorf (Celestial Teapot Software) is probably best known for creating Fluid, a Site-Specific Browser app that we love to talk about. While Fluid was a great and well-executed idea, Todd's latest app, Fake, is truly inspired. The easiest way to describe Fake is to say it's Automator for the Web. It may not have the mass appeal that Fluid does, but its target audience (Web designers and developers, as well as Web power users) will have no trouble appreciating its capabilities.
You can drag together a basic workflow, say, to automate navigating to a form and uploading a file. Add in a repeat loop to stress-test the uploader, insert some conditional logic and error handlers, and then load it up with assertions. It's not a substitute for user testing, but it's close, and it can help you squash bugs that you normally couldn't spot on your own.
Even if you're not a Web developer, Fake makes simple work of tasks like filling out repetitive forms, regularly searching for text on websites, and even capturing screenshots. It's powered by AppleScript, so it's easy to incorporate Web automation into just about any aspect of your workflow.
Fake is well-documented, and help is available within the app. If you try it out, be sure to read through it, or you might miss out on less-obvious features like "Connecting," which lets you control drag from Actions to live elements to make connections, Interface Builder-style. Todd is also compiling some video tutorials on Vimeo, so check those out, too.
You can download a free trial from the Fake.app website. The trial has some limitations (eight-action max, and you can't save workflows), but it lets you explore the possibilities. For full functionality, you can purchase a license for US$29.95. Depending on your needs and current processes, Fake could easily shave enough time from your current workflow to justify that price in a week. I recommend checking it out!