Very handy tool that allows one to preview a site as it might look in a variety of browsers on a variety of platforms. Clever.
Selenium is a test tool for web applications. Selenium tests run directly in a browser, just like real users do. It runs in Internet Explorer, Mozilla and Firefox on Windows, Linux, and Macintosh, Safari on the Mac.
How to install Internet Explorer 6 and 7 side by side. *Very* useful for development and testing.
twill is a simple language that allows users to browse the Web from a command-line interface. With twill, you can navigate through Web sites that use forms, cookies, and most standard Web features.