Web Browser Emulators
How to Use BrowserCam to Review Your Web Site
BrowserCam is a helpful tool to review Web pages in many different browsers and operating systems. It helps you find problems with your site that you might not otherwise have known about.
Sauce is a tool to help you test your web and mobile applications on various systems including Windows, Macintosh, Linux, iOS, and Android. There is a free version, a desktop app for Mac users (and one in beta for Windows) as well as online browser access.
AnyBrowser Site Viewer
This is less of an emulator, and more of a suggestion. AnyBrowser has a specification that is loosely based on HTML 3.2. The premise is that if your page shows up in their harsh spec, it will display for nearly anyone.
Backward Compatibility Viewer
Doesn't emulate browsers so much as HTML elements that browsers might not support. You can see what your page will look like without them.
Play with really old browsers like NCSA Mosaic, Lynx, and HotJava.
Lynx is a text-only Web browser.