CameraSim: Learning DSLR Settings in Your Browser
"So you've been thinking about getting a DSLR but you're not sure if you're ready to step up to a heavy-duty camera. If you don't have a friend who can teach you how it works, or you'd rather learn on your own, CameraSim can give you a pretty realistic account of what it's like to use a DSLR-but in your web browser."
If you're new to using a digital DSLR - or, more than likely if you're reading this site, you might know someone who is - this Web-based tool allows you to see that impact of using various sliders that emulate camera ISO settings, aperture, and shutter speed. Pretty slick!