If you do serious web development, you sure have multiple working environments. This is true for ruby on rails, but I’ll guess you’ll do the same using other frameworks or languages. I’ve found a quite useful Firefox extension to switch from development to production (and back) with just a click (or a keystroke: Ctrl-Shift-X): Server Switcher

This is helping me redesigning the MySQL training part of our website, and can be useful in some other situations.